BJ, I have put a little liquid auto wax (Turtle wax or whatever) in my media, and it seems to prevent tarnishing pretty well. I use a vibratory polisher and just squirt in a little of the wax as it's running. At first it will "ball up" the media, but it works its way through all of it after a few minutes. Don't use too much, just squirt a light bead around on top of the stuff. You can add more if you want, but you can't take any out!
RonF