I have those dang things on my '09 Grand Cherokee, and had the same issues you speak of, until I started using Tuf-Shine products. They sell a cleaner for the entire tire and letters, then you put on their clear coating on the white letters first, let it dry, do a 2nd coat, let it dry, and then do the surrounding black part of the tires.
If you hit the rwl's by accident its no problem because you sealed them beforehand, so they wont stain. The clearcoat product lasts a long time on both surfaces and is not greasy, etc., at all. Their tire brush is really great and they sell a couple of different sponges that are really great too.
Dan F