I work in clay a good bit. I use Klean Klay I get from Dick Blick; it's the lowest price anywhere. They call it Blick gray clay, or something like that. It's a no sulfur clay, which is necessary if you are going to make a rubber mold.
There is a European web site that has models. This is the link for the female site but you can get to the male site from there.http://www.female-anatomy-for-artist.com/?id=16&page=34
You can join for one month for about $40 US. The advantage there is that they have the model on a turntable and take photographs from every 45 degrees of the same pose.
I make smoothing tools from common builder's supply silicon caulk. They are flexible so they don't dig in. Also to finish it off I use naphtha (or Coleman camping stove fuel) and a fine brush.