I'm not sure if you could get it going fast enough without killing your hands...
What about a cake mixer (hand held one with the two steel attachements that come out?) I got one of those at Go-Lo for $8.99
Yes, exactly that type of store, you know the ones full of "junk" but we always seem to buy heaps of stuff in there.
While you are in there, check out the kitchen section, they sell a lot of those silicone moulds for like $2 each.
I got some of the loaf style ones, they are perfect for soap.