It's a pain to do, but waxing them will help by beading the water off the waxed area, helps with water reflected glare too. You'd have to experiment with the type of wax and application so it looks natural. I used spray can Thompson's waterseal once years ago but I can't remember the details of how well it worked, actually it worked, but I can't remember for how long. Problem is, if you want to re-paint or touch up, you'd have to remove the wax. Like I said, a pain in the neck., lol
Oh, by the way, this is a nice site, just got validated so you'll see more of me bye and bye.