What Poser version? In Poser 5 you may be able to do it by blending in a noise noe or something. But you really need some sort of paint program. Do you have any? like PaintShop Pro - or GIMP? (not sure if GIMP can use Photoshop brushes, I think not but the program itself is free and col :) )

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.