hiya,
i was just mentioning a way to do Wrinkles in skin. if you take a piece of Sculpey and a tool, then draw some lines in it, you will notice that the lines are deep and the passing of the tool on the surface leaves debris or tiny bits of putty.
But if you take another piece of Sculpey and place some Sandwich Wrap/plastic film/food bag over the putty and draw the same lines as before, the result wil be smoother and the line much finer. i first saw this methods on one of John Brown's dvds (figuresinfocus.com).
all the best --- tim