I used Super Sculpey. I mixed it with some Black sculpey to get a grey color, mainly for visualization purposes. Grey catches lights and shadow easier.
It's about 5 inches tall, no intention to make the body though. It's still at an early stage, I have not finalize the details , still thinking how I should finalize his head. Currently I had his brains exposed. : ) Probably some hair. But I do not want him to look like the Green Man.