[soundtest]

I used to work in animation. You might remember me from such shitty cartoons as The Ripping Friends, Hoze Houndz and Maggie and the Ferocious Beast!

We used Softimage Toonz x-sheet module for compositing (which is what I think you're talking about), but from what I've heard After Effects is better and more user friendly. Softimage Toonz has different modules for every aspect of the animation process - scanning the frames, ink 'n paint, digital x-sheet, and batching... but it's a really weird program to get used to... it's compatible with Windows systems but wasn't really designed for them...

You seem to have a decent idea of what you're doing already though, and there's not really all that much to know besides learning the software. :/