Silent - I went with soft spongy wet n dry sanding blocks (the really fine grit ones) and a little bit of oil
got a mate who can packerize it and respray it so I just went for it while I had it knocked together on a dry build (was going to add the serial numbers and flatten some of the domed rivets etc - so finish was going to get redone anyway)
BUT I ended up quite liking the effect, so I'll probably just leave it as is
cheats way of getting a weathered AK but I didnt fancy twenty years of carrying it around to acheive it naturally - first day out doing the shopping with i