YThe grease thing got me thinking. In fiberglass work you use something called mold release(PVA, polyvinyl alcohol). Goes on and dries to a thin film and can be washed away with water afterwards or even peeled off.
PVA is basically any of the white glues, Elmer's, Titebond, etc. (think woodworking) I thought maybe rubber cement could work. In grade school, we used to paint it on our fingers and gross the girls out by peeling it off once it dried. As long as the glue doesn't attack what it's spread over, it should work.
