I am currently repairing an Olds Ambassador cornet with stuck slides. The previous owner jerked so hard on the tuning slide that he broke quite a few solder joints and bent the snot out of it. I grabbed the wrong can and accidentally sprayed Gumout on it. A couple of light taps with a mallet and it popped right out. I'd be careful using Gumout, though. It would probably take off some lacquer. So would WD-40.