all good advice, but I'd use a shotgun bore brush spun in an electric drill, myself - along with Kroil, WD40 or whatever was handy. Since Kroil isn't available in Canada so far to my best recollection, I'll save what I've got to mix with my Butches Bore Shine for my modern gun barrels, and use WD40 on the mould. I've cleaned them with 4-ought, but be careful to leave the edges of the ball 1/2's sharp, not rounded.