This would be pretty dangerous. Flash paper/nitrocellulose burns VERY hot, VERY fast. Depending on the fabrics around it, it would be entirely possible to light the whole thing up.
I've seen a poorly chosen shirt melt onto a fire performer's skin in the past, it's not a pretty sight. A single ember can cause a hole the size of a basketball. I've also seen flash paper create second degree burns in less than half a second.
If you wanted to do this, and I am by no means endorsing that path, you'll need to make sure that the area between the flash materials and the skin are thoroughly insulated, and also that the path the fire will take (generally upwards) is also insulated. Keep in mind hair is extremely flammable.
I would say decently thick leather, or wool, would be sufficient. Kevlar would be better. I wouldn't use silk.