Brownell's release agent is a plastic dissolved in a thinner, and cures up into a filmy bluish plastic. It comes off very easily. If he used wax, solvent alcohol will take out whatever you don't sand off. If he used silicone, you will have to wipe the barrel channel out with something a lot more aggressive, like acetone or mineral spirits. Don't worry about the laminated stock, though, it will be fine.