To answer that is a LOT more elaborate than I would be able to post here right now, but Nem pretty much got the jist of it.
The idea is that you can use an animated alpha map to "fade-away" your clothing/objects, and the cool part about that is that you can link a particle emitters' rate/color/whatever to that alpha.
So, when the alpha starts "wiping" your color channels away, you can tell a surface emitter to emit using the shape and speed of your alpha.
Alex A. of Gnomon has a free tutorial covering this idea when he talks about Gravity and Uniform fields at his site.
Check out the SIMPLYMAYA tutorial links database for the link to Gnomon, then find thier free section for the article/tut.
It is about making a jar "blown-away" by wind, but the idea is the same.
Lemme know if that leads you down the right path
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS