I have a 2 year old, quality built, expensive euphonium, but recently I've had problems with valves 1 and 2 sticking in the down position or sometimes being sluggish despite frequent oiling and cleaning and installing good springs. Perhaps it's because I don't always keep my fingers "on center," although I certainly try not to stray too far off.
I had a similar problem in an old Conn euphonium that had sat unused in my basement for a few years. I used Brasso to clean the valve casing of one of the problem valves. (I poured some on an old sock, put the sock on a wooden stick and rubbed gently against the inside of the problem casing.) After I thoroughly cleaned everything up, I haven't experienced any more sticking problems.
Should I try this on my newer, more valuable instrument or leave it to a pro?