It's actually not that hard to do what Loomis says, if you put it into practice whenever you can.

That is a rubber ball cut on the sides, simulating to be the skull.

I don't know if a piece of wood will work for you, I think it's better that you look for something round and cut the sides like I did, and when you have your model, try to move the ball according to the position it has, and that way you help yourself plus.