Just spray the foam in a desired pattern. let it dry for 30 minutes.
Coat in black, then highlight red and you are done. add any last details and you have a severly bad burned costume.
Due to its adhesion, the foam will stiffen to the shape it was in when you sprayed it. this is a good costume to do even for a prop for your front porch or household haunt. red light and blood, and there you go. it holds good shape, just ensure it with a few pillowsbefor you spray the foam and the original relistic body form willstay.