Been meaning to start sculpting seriously. I sculpted a Marcus Aurelius bust for a Gladiator play produced by the Department of English in my college. Back then I had no idea how to clean it and just cleared up stones and hay and began sculpting. So I couldn't get fine details. 
Now I thought I'd be more specific in what I do. So I got some rough natural clay. Diluted it (one forearm pump it was), poured the mixture through a sieve. Then again poured it through a cloth for more clarity. Now the clear clay water needs to dry up. Hopefully it'll give me a smooth texture.

Pictures,
Left - hard clay
Right above - filtered clay chocolate 
Right below - half way through mixing clay and water.