[Graziano Pozzoli]

Hi Chris I found this tutorial by Eran Stern on Creative Cow very useful; may be it could help you.
Adobe After Effects “Invisible Cape”
In this video tutorial, Creative Cow contributing editor Eran Stern with the help of his brother Yuval will show you a simple method to create the famous invisible look inspired from the movie The Predator.
Tutorial, Video Tutorial, Eran Stern

Graziano