Here, I'll lay out the process in a nutshell-
Make the positive mold out of clay (it can be trashed and reused afterwards since its ceramic clay that hasn't been baked),
Then you cover the clay in 4 layers of silicone in order to make the negative for casting.
Since the silicone isn't very stable, but captures the details and undercuts you need, you have to make a stabilizing shell. I just used plaster for this because it holds its shape well. You'd need to make two have to remove from eachother so that after casting, you can actually get the finished product out.
Finally, its time to slush-cast the resin, in which while it hardens, you swirl it to distribute it evenly.
After the curing etc, you have a hollow, resin mask for fursuit making, that can be dremeled for eyes and hinged and cut for jaw movement, then furred and ready to go ^.^
It's a lot of work, but I think its been fun and fascinating.

That's a pretty involved process indeed! Still, I'm sure that it's probably a better option than carving out foam though, right?

Carving out foam is good, but with resin you can reproduce as many as you want of each blank :3. It makes it more feasible. Also, the jaw movement is much more articulate and is pretty much guaranteed to be in alignment, and jaw movement is something that I love in suits xP.
Also, resin is much more durable and lighter than foam, and it also doesn't trap in all of that heat. Personally I think it looks better and is just more functional O.o.