Use Various Flavors of Jello/Gelatin to create edible scabs and road rash effects:
Peach, Lemon, Orange, Grape: skin growths, foundation for scabs, blisters, scars
Black Cherry or Cranberry with a teaspoon of Grape mixed in: blood, veins, moles, road rash
Lime: boogers, pus, various marine life (algae, seaweed)
Plain: create the foundation for scars, scabs and other creations; dribble colored gelatin over the clear, shaped foundation
