I have some basic care tools that I use to maintain my instruments. Key oil, cork grease, bore oil etc. But there are some things that I have found to be very useful especially in buying a used contraforte. The contra was in the use of Lewis Lipnick, a very accomplished and busy player. It had some tarnish on the keys, and I don’t trust myself to take it all apart to clean it. Contrabassoons and contrafortes also suffer from water problems. Contra is the only woodwind instrument that never EVER gets swabbed!
I found these silver polish strips to be amazing! You get a wet paper towel, wipe down the tarnished area and then just wipe it with the polish wipe and its done. I also have “acidic hand oil” like we all do, but mine can damage the plating of instruments over time. So this is a very easy way to keep my keys from damage. These I found at Bed Bath and Beyond
The other great find is Silica gel packets; this is a form of desiccant, or a chemical that removes moisture from the air. I bought a couple packs of these and I keep two in the contra case at a time. When the contra is put away in the case, the instrument is still filled with moisture and warm moist air. These packets help dry out the air inside of the case. I bought mine off of Amazon