If you own a decent quality one, you've done all you need to do. One item about RainX. Some plastics can be discolored by it, and if it does discolor yours, you need a better antenna. HiQ, High Sierra, and Tarheel all use either Lexan or Acrylic outer covers, and are impervious to RainX.
Alan, KØBG
www.k0bg.com