Soapylove book, I repeatedly use my favorite soap making tool of all time - my silicone brownie pan which I found in a discount store over 4 years ago. It's not just any silicone pan, though. It's shiny on the inside, which creates a super slick and glossy surface to all soaps made in it.
That's important to me because when projects involve embedding, layering, clear effects, or swirling, I want that to be easily seen. A pan with a dull or matte inside will make the surface of the soap seem like you're looking through frosted glass. If you would like to pick one up, they might not be easy to find. The pans from Wilton are matte, for example.
Here are some that will work great. For the same exact pan I use, pick the one from Orka. For a less expensive version, the line from SiliconeZone all are shiny. Then, for fun, you can also get shiny silicone loaf pans which are very super easy to unmold and amazingly durable, and tons of other shapes! Happy shopping!