This is a process called wet forming. In order to shape leather for a mask, or any other item where leather is shaped (like leather roses, bowls, etc), you have to wet it all really good, then shape it. After it's dry, it retains the shape (in the case you mentioned, of the mask)
Leather is generally wet to some degree to work on though - it's called "casing". Personally, if I'm doing a smaller piece, I only dampen it with a sponge. If it's a big piece, I'll soak the whole thing and then let it dry off before I wet it again with the sponge to work on. Wetting it that way lets me see if there are any flaws I'm not noticing.
That's my .02
As was mentioned, check out the Biker/Tattoo section, you'll see some nice flame work. It's in the adult area, so let Johanna know you want in to see it.