Wow check out Sculptris it’s a FREE 3d virtual clay application similar to Mudbox or Zbursh, that allows you to sculpt and paint in a very intuitive manner, it’s created by Tomas Pettersson and is only about 3MB in size. I would definitely recommend downloading this and if you enjoy it giving the guy a donation as he has obviously put a huge amount of effort into it. (Only runs on Windows AFAIK - sorry Mac users)