Molding? Whoa, way beyond my expertise.
Since this is a modification of an existing Robin figue, I'm not baking him, but boiling it. Not sure how the make-up or chalk would work with the water.
I'm going to need a combination of matte and shiny surfaces, because I'm making a Steppin out Robin. On the stepping out figures, the suit is flat, but the lapels and vest are shiny