Twollow goes along with the growing tools on follower management that we list. Unfortunately this one costs money, where the others are free in most instances. Costs range from the 7-day trial with limited function to the Gold 34.99/month or $149.99/year package.
The number of keywords you can use is based on the package you purchase and range from 5-20. All will auto-follow people and provide filters and user management. Unlimited auto-follow is restricted in the trial version. The only real difference between the packages is the number of keywords after viewing their grid.
I think you could accomplish this task with other free tools, but let us know if you use them.