I'm no expert, but I sure know what NOT to do to a horn from experience, so here goes:

1. NEVER use a Scotch Brite Pad to clean spring cylinders or tuning slides. It leaves abrasive grit that compounds the stickamongus, and is very tough to remove. Darn stuff sure gets the surface shiny, though. Anybody know a good way to get similar results without the gritty residue, please enlighten me, as I could use a fair piece.

2. NEVER use a monkey wrench to loosen a sticky bottom valve cap. This will deflect the tender roundness of the valve casing, and cause severe valvus stickamongus.

3. NEVER use a case that your horn's valve stems will not align perfectly with when closed. Tempted to say never use other than OEM cases, but there are enough good ones out there, just be careful everything aligns properly when closed.

4. NEVER oil valves from bottom valve caps. The part that needs oil most is the metal piece on the bottom of the spring, along with the slots in the spring cylinders, which is where the movement is taking place. Not sure about oiling other parts of the valve, could use some advice here meeself. Also believe regular wiping off of old oil and replacing with new oil is recommended, more often if you put a lot of mileage on your horn.

Thanks for bringing up an interesting and annoying problem!