Have you ever heard of Simichrome? It is a pink polish that comes in a tube, made in Germany, sort of pricy for what it is. I think you might be able to buy some at Brownell's, but I'm sure it's available from many sources. I used it for years to polish brass. It just takes a very small amount and a very soft cloth. You might give that a try, and then follow sawzall's advice about using a paste wax. Several of my guns are preserved with Trewax brand carnauba wax. I put it on both the metal and wood. You don't want to overdo, just a little bit put on the surface you desire to protect, rubbed with your finger in a circular motion to fill any pores. A very thin coat, which you can repeat as needed. Let it dry, which only takes a few minutes, and then buff it off with a soft cloth. You'll get a hard, shiny surface which might very well prevent re-tarnishing. Wax was widely used as a protectant before all of the miracle oils appeared on the market. One nice thing is that it's easy to touch up or apply another coat as needed, and as long as you keep the coats thin and don't just gob it on it's not noticeable and enhances the firearm's appearance.