While you can generally remove your cast models from flexible molds without much trouble, non-flexible molds may require a release agent to help you free your sculpture. A variety of commercial products are available for this purpose, but you also can make your own release agent.
What can I use as a resin mold release?
Nonstick cooking spray, available in most any grocery store, works as a suitable resin mold release agent. It's nontoxic and won't harm the resin or the mold. Once you remove the resin creation from the mold, wipe the cooking spray off the resin and the mold using a rag.