When I wanted to make a one-off cowl mold a few months ago, I was in the same situation. After a little research, I discovered that Johnsons Paste Wax is almost (if not all) 100 percent carnuba wax. My plug was constructed from the green florist foam, but the surface was pretty unstable, so I coated it with finishing resin. I still wasn't happy with the plug surface, so I covered it with aerocote lite, and then applied 7-8 coats of Johnsons paste wax. Although it was a little sticky getting the mold off the plug, it worked adequately. I then used the Johnsons to wax the mold, and again it worked adequately. I haven't tried to pull a second cowl yet, but I'm guessing it will be a little easier the second time around. For release, I went to a local craft store and found a spray mold release (I think it was in the ceramics section). It doesn't say what it is, but it looks like its probably PVA. A 4 oz bottle cost a few bucks, but it worked along with the Johnsons paste wax.

Brad