Polishing my Motorhome

I'm new here, but an avid forum user elsewhere. 

You keep a car clean by using a good polish, which makes the rainwater run off. What's appropriate for the GRP(?) body of a motorhome?

Somewhat related... do aquaphobic coatings have a part to play? The "H" logos in the middle of the wheels of my Honda Legends never get dirty, whilst the rest of the wheel gets filthy in a few hours. I doubt that the logos are aquaphobic, but it got me thinking, and now I'm one of  the frustrated/tantalised shoppers in this arena.