I've used waxed paper quite a bit as a release sheet. It can get stuck in the epoxy if it's part of a heavily clamped stack and you leave it until complete cure. But it stays flat better than plastic film so there are few wrinkles in the cured epoxy. On the whole, it works for me. For the puzzle joints, I put a piece of waxed paper on the working plywood surface under the planks, then the puzzle joint, another piece of waxed paper, a 2x4 for clamping, and screws through the 2x4 into the working plywood to clamp. BTW, the puzzle joints on the skerry took some stout whacks with a rubber mallet over the waxed paper sandwich to get the fingers all flat together.