urethane resin is notoriously hard to paint. i heard about the trick where you prime your mold then cast so that the resin sticks to the "back " side or "inside " of the thin skin/shell of primer. One guy said he would dry brush gesso into the mold. I used my airbrush to mist in several light layers of primer. i let this dry, cast, and like magic have a urethane cast ready to be painted with acrylics. i think i'm going to do this with my new line of lil toys i'm working on.
skin is hard to get right. not saying i did. sigh. painting two furiosas at the same time took me almost 3 days.