This Spanish language tutorial by Aura Prods claims that Lockdown is the best plugin for After Effects and it does a great overview of how it works and how easy it is to use it. You can use the caption -> auto-translate feature if you want to follow along in a different language.
This tutorial shows how to track a full face and body with Lockdown. It combines the usage of the Ae built in Face Tracker, Mocha, and Lockdown's own tracker. This tutorial shows the advantages of each type of track, and how to combine the best of all 3.