I use a generous coating of Partall wax, from Fiberlay, and I also put down a sheet of parchment paper. The parchment is really the savior, but if it happens to tear and a little gets through, it pops right off with the partall on there.
I to can vouch for the partall. Haven't used in in ski building, but used it, and the fam uses it in many fiberglass aircraft part molds. Haven't had a part stick to date.
I've been using Meguiar's Mirror Glaze maximum mold release wax for a few years now, works great every time. There's always a bit of clean-up, but extremely minimal.