If you're willing to spend a few bucks, the fastest and simplest way would be to go get Phil Cooke's Poser Toolkit; it has a shrinkwrap script that will do exactly what you want, independently of the cloth room, gravity, and the like.
http://www.philc.net/PoserToolBox.htm

Right at the top is a video of the shrinkwrap tool in action.  $40 US.  Also has tons of neat little utilities e.g. a script that exports all the bodypart morphs for a whole figure as a group, in one operation.

edit: oops, it's not a video, but still very clear:
http://www.philc.net/PTB_tutorial1.htm

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