I have a Reynold's cornet. I play sometimes, but my son's in beginning band and these days he plays more often than me. The 3rd slide has this annoying problem of sliding out if gravity allows, which it does. (He is not yet in marching band.) After awhile of playing, every time he plays a note with the 3rd valve, it's really flat. I have taken the horn to a repairman. (The same, who "fixed" my horn valves by oiling the entire instrument on the outside.) I have wiped off all grease from the slide, but it still slides. There is shiny metal and dull metal on the slide. It only slides for the length of the shiny part and stops. There is no ring for the finger to use to hold the slide in. There isn't a screw thingy do to add a ring. Is there anything to do to the slide to prevent it from sliding? I was considering duct taping it in, but then the boy won't learn to adjust slides as he plays. There are some spots of red rot on the horn. It's old. Is there anything I can do to get it off and to stop the spread? Pieces of lacquer are falling off. I was thinking I'd like to put a leather gripper on it to keep my son's hands off the raw brass and to hopefully stop more pieces from falling off where the hands go. Is there an economically priced gripper? anyone tried making one? Thanks for the help!