I might be able to help you out, I'm getting the CNC router up and running over Christmas. Plan is to cut foam for now but might move to MDF and Corian eventually for female molds. Really you don't need a mold for a flying wing, foam does fine.
Still, if you insist, make the plug as smooth as you can. Hand sanding molds is a real pain, but done right you can get some nice finishes. This is wing #5 of 18, before the PVA was removed, so its still dusty.
