I dont use a crockpot. I've got an old coffee tin that I put in a boiling pot of water like a double boiler. Get it melted, turn the temp down and just let it sit for a while. Hang to dry.
Molten speed wax is cool, but I actually just use gulf wax which can be bought at any large grocery store in the area by Mason jars and other canning supplies. I use the wax many, many times and typically just top off with more. Dirt settles to the bottom. I've got a full document on my process if anyone is interested.