Don't know what you are using that acetone doesn't remove, but I wouldn't use it. I use Jerrows, I think you can still get it from Track. One brush full should last for most of the gun. A little goes a long way. Removes from metal easily with acetone and even from wood if it is fairly smooth, won't get it all out of end grain though. Another option is to take a small, 1-2 ounce jar with a metal lid, punch a hole in it and make a wick out of a rag. fill it with mineral spirits and light. It makes a very smoky flame that will leave a nice mark as well. I know some people swear by candles and have great results, but I can never get enough smoke out of them.