Mask Effect to make person disappear

[Mark Suszko]

Actually, I would not do the effect you want in Motion, not under the circumstances you describe. Instead, render out the shot from yuor timeline as an image sequence of high quality stills, say, in tif or targa format. Take that folder of shots into Photoshop and hand-paint your guy out using some of the particle type filters in photoshop as well as the cloning tools in photoshop, to replace the background hole after removing the actor.

This will not be fast or fun.