oil based clay to use

I use Klean Clay for my sculptures. You can order at sculpt.com or other places. I order directly from the company that makes the clay.
Reason for this- I use grey clay-ex-firm, You cannot buy the grey clay in ex-firm unless you ask for a order from the company, you have to buy 350 lbs.
I think it is worth it for the money you save in the long run.
You of course can re-use the oil-based clay over and over again.