Why don't you try WED (Walt E Disney) clay?
I've used Chavant and even though I love the results, it's really hard to work with and expensive.
After doing a lot of research on different make-up/SFX forums I switched to WED clay and really, really like it especially because it's really cheap.
I bought a 25lb block for $13.00
I went to the Imagine-Nation Expo in Vegas back in '03 and both Steve Wang and Jordu Schell used it on live demonstrations. Someone from the audience asked if they use WED all of the time and both said yes. That was good enough for me.