I am using Quick Wood Putty found at Home Depot. It comes in a small tube. It's a two part putty in one bar. You pinch off however much you need and kneed it into one color, then you have about 15-20 minutes to sculpt. Vaseline helps you tools slide along the suface. Because of the working time, I do things in sections. Once it's hard, it bonds and is extremely durable, can be Dremeled and sanded. I like to work with this stuff because you don't have to bake it or anything. I also like how it starts out very soft for basic detail layout, and hardens slowly as you refine the detail allowing for harder pressure and sharper tools until you have some sharp details working.
I have never had any of my sculpted areas fall off or peal at the edges, but if you mess up the sculpt or run out of time, it will pry off without too much brute force.