you know in particular, is it possible to isolate the particles created on collision?
if so you could make alot of collusion particles using an appropiate texture layer
and then use that pre-comped layer in a new layer and apply mecury or even median/level
to tweak.
im not saying this will be good but its my thoughts on how the tacle this.
good luck and mail me if you have a result on that please.
graham
life is breathtaking!