Best way to get oil-based clay off a mannequin head?

How do you guys get the clay off your mannequin head when you're done with the sculpt?
I lobbed off all the big stuff, but now there's a ton of little pieces stuck to it all over. Whenever I try getting them off, I end up just smooshing them around more. I want it to wear my mask while I'm working on it, but I don't want any clay to get inside my mask. What do I do?