I've never done any kind of casting before. It turned out to be quite simple (with the help of a few hundred questions)
Here's the latex I bought from Cementex. The top container is the latex itself and the bottom container is the filler.
I mixed them 50/50 to give me a fairly hard latex cast once dried. The directions on the container said two to one, but I was assured (thanks Ralis) that 50/50 would be firm enough (He was right! Like a rubber ball!)
Here's my first pour (OK, so I slopped all over!) I tilted the mold around a little to make sure that there were no air bubbles.
Here's my first pull! Ain't she beautiful. This is the large skull mold from Nowell it is number 750. For some reason you can't order this on line at their web site, but I called them and they were more than helpful.
This is their 1749 mold. A smaller, more meanacing skull.
TA DA! Needs to be cleaned, but I'm very happy with the results. If you are interested in trying this, go ahead, don't be afraid. It was a lot simpler than I thought it might be.