Prop as in cinema? Or Prop as in Boat propeller?

For my RC yachts I use this nasty green stuff. I forget the name, i get it from the hobby shop, but it's been around a while, and it's got some chemical that's a skin irritant, but it works like bondo, pretty cheap, and is specifically made for plastics. Sands down easily and paints very well. I guess it'd work pretty well for stage props too I guess. Or you could be making a prop prop.

After a bit of googling, it turns out it's called "green Putty" by MMD.