I once had this clear antenna spray paint I got in a pot luck box at the local big electronics store. I used one of those "chain link" stainless scouring pads and then sprayed the feeds with a light coating. Worked fine. But you do have to get all metal particles out of the tube before spraying.
Since I have run out of the spray, I have been just using the scouring pads. I have toyed with the idea of car wax in place of the spray, but never did it