Has anybody ever done this? I'm asking because I have a small area on a the first-valve tuning slide that's worn through. I was thinking I could simply polish it, then airbrush on some metal-friendly lacquer to protect the brass until I can have the damage properly repaired (instrument repair facilities and personnel are very hard to come by in West Texas - a.k.a. around 90 miles from the Middle of Nowhere). Any advice would be welcome.