Here are a few suggestions given to me by an emergency room nurse. She said they have used these ideas in training their emergency responders.
 
Use a little thicker mix of instant plain oatmeal to simulate skin sloughing off after a burn. I tried it to see how it looks and it is pretty good. Takes a little bit for it to dry but I aided the drying process by using a blow dryer.
 
I have been experimenting with adding bruise powder, ash, charcoal bits and such for effect. Also use spray insulation for blistered burned skin (the type used to plug holes in siding.) Haven't tried this one yet but I have a small container of it ordered through my hardware store.
 
Joyce L Nobles
Clearwater County
CERT/TEEN SERT
Instructor