While I would never recommend that anyone fully automates their SEO, There are tools out there that can do some of the somewhat tedious parts of the job. When it comes to building links for PBNs and lower tier websites, there are tools out there that can automate a lot of the outreach, which allows you to carry out a lot more work on websites that usually requires lots of staff or VAs otherwise.
SEO AutoPilot is one of those tools. It is a piece of software that you install into your computer, which carries out link building on high authority websites, that are google indexed, all while staying Google safe. This tool is very simple to use and does a lot of the work for you. One thing to note however is this tool only works on windows or running a VPS on a Mac. (so keep this is mind before purchasing)
Price
SEO Autopilot has 2 different pricing options for you, monthly billing or a lifetime purchase.
The monthly option will cost you $149 per month, however they do run deals often and as of this review date its currently on sale at $99 a month. If you'd rather pay a one time fee and own the tool for life then it is going to be a quite a bit more expensive, this will cost you a total of $1897.
There is a trial period available for 7 days that will cost you $1 a day so you can opt out before paying the full amount. This will let you really try and test the tool before committing to buy. The option is also there for one-time payments in which you buy a set amount of campaigns. This again is useful for those of you who maybe don't have a lot of PBNs and are looking to prop up a couple of websites.
Proxies
Before you use SEO AutoPilot, to get the best results you really want to be adding your own proxies. There are loads of places that you can buy proxies. I recommend using the site buyproxies.org. 
You have the option of either semi-dedicated or dedicated proxies. It's entirely up to you how many you buy, the more you buy the more campaigns you can run simultaneously and faster it can operate.
For example if you're only run 1 campaign at a time then 10 proxies will be enough, however if you want to run 4 or 5 then you'll need a little more, I'll explain why a little later on.
Once you've purchased your proxies its time to add them to SEO AutoPilot. Along the top is a settings button, clicking on this will bring up a box with tabs across the top. Click on the proxies one to bring you to the screenshot above. When you receive your proxies there will be the following details ipaddress:serverport:username:password.
Before pasting your proxies into SEO autopilot, make sure that they are arranged in this format. Then clicking on the "test proxies" button will check to make sure that all of them work against Google. Now your proxies have been added you're ready to start your first campaign. 
SEO Autopilot has lots of different templates that you can use. There is a dropdown menu that contains all the diagram types available, each of them has a little description telling what kind of link will be acquired as well as which tier it sits on. There is also a "Diagram Editor" which can be seen at the top right-hand corner, this lets you build your own diagram from scratch or edit a pre-existing one. 
Once you've determined what kind of links are going to be in your campaign, you're presented with the screen above. There is a lot to work through here so I'll start by explaining some of the sections. On the left-hand side, there is a big list of blog websites, each with their domain authority listed. If you scroll down this list you'll also see more dropdowns with all the different link types. These are the sources used when you implementing any of these strategies in your campaign.
If you don't want to use any of these platforms then you can deselect them with the checkboxes shown. On the right-hand side, you can change the diagram structure (Doing this will wipe out any data you've filled out in the main section so if you're going to change then do it sooner rather than later!) You can also set your captcha service along with the number of threads you plan on running. The captcha services that SEO Autopilot allow you to use are:
- 2Captcha
- Imagetyperz
- RIPCaptcha
- AntiCaptcha
- XEvil
Each of these tools have their own pricing schemes, I would personally recommend 2captcha as 1000 captchas will cost you around 40p These default settings are okay if you don't have many proxies, if you have hundreds then you can definitely up the number of connections at a time.
It is also possible to schedule your posting here, as default SEO Autopilot will instantly begin posting once you start the campaign, however you can set this to run for a set amount of days and how often to post etc. Spend some time getting these settings to how you like and then it's time to move onto the main campaign data. 
At the top you'll see a list of tabs, depending on what strategy you have in place you may see more or fewer tabs here, essentially this is separate menus for each of the link types.
So what you have to do is work your way through these one at a time, if it's your first campaign it may be best running a simple one that maybe only deals with web 2.0's so you can get an idea of how it works without getting overwhelmed. I am running a simple strategy for this example labelled Corus.drgm.
Common
As the name suggests, these settings are used in every campaign type there is (money site settings). If you have ever used tools like GSA then you will be quite familiar with this layout. At the top is where you would place all of the money site URL's that you want links for, and underneath this is the list of keyword anchor types.
It's up to you which ones you want to use, all of which have a percentage option so you can choose the keyword type used more and less frequently. I personally try and include as many different anchors as possible, Google love to see variation within a backlinking profile so when using a tool like this it's important to try and mix it up as much as possible.
Web 2.0 Blogs
These are blog posts set to be published on all of the Platforms that you leave checked on the left hand side. If you want these links to hold any sort of value then it is important to fill out all of the information here with unique content. SEO Autopilot gives you a few names and subdomains as default, however you need to think about the number of people that also use this tool and have used these exact settings.
There are a few ways you can go about getting this content. You could spend some time thinking up a list of names that you can import into SEO Autopilot or you can Google example name list's you can find files for download that will contain all of the example names you need. Either way it's very important to get a list that will ensure all of the articles you post are unique leaving no obvious footprints for Google.
The other part you want to take care at here is the quality of the articles. I would personally suggest spinning your articles on a 3rd party tool instead of using SEO Autopilots free spinner. The free spinner will do make your articles unique but the overall readability isn't the greatest, you can get better results using tools such as WordAI which can actually be used directly from SEO AP if you have the API credentials.
Social Bookmarking
This one is very similar to the Web 2.0s. Again you want to make sure that your social bookmark title and descriptions are unique. 
As I said in the previous section, there are a few different spinners to choose from. A well-spun description will help any links you get here carry any sort of weight.
URL Shortener
This is the last section of my campaign here. SEO AutoPilot sets the URL shorteners for you so there isn't much to do here. Once you've filled out all of the tabs on your campaign, you're ready to start. All you need to do is click the "create" button on the bottom left. This will run the campaign on whatever schedule you have set, now you wait on the result to come through.
Results
As you can see it has run the campaign successfully, it gives you a list of the overall sites that were submitted to and the number successful. This campaign ran quite well with only a few submissions failing which is always expected. This was just one example of a campaign being run, you can set up far bigger campaigns using all of the different templates SEO AutoPilot has to offer.
Conclusion
SEO Autopilot is a great piece of software that helps you retain a good amount of link building on all of those PBN sites that you have. While these links are by no means the most powerful, putting in the right steps in your variety and article spinning can get you a good amount of power that will definitely benefit your lower tier sites. If you are someone that is struggling with the upkeep of your websites then I would take a look at this tool. With pricing schemes that allow for one time buys on campaigns and a 7-day trial, SEO Autopilot is definitely worth checking out.