I can't think of a topic that provokes more strongly held but totally opposed opinions than this one.
So here's my advice:
1.Get rid of the full width rear guard on the motorhome. It just kicks up more rocks. The hula skirt is useless also.
2.Don't use a car bra. A stone lodging in there will scrape things up worse than anything.
3.Protect-A-Tow or the similar Tow Defender will cut down on the debris being kicked up onto the toad.
4.All toads will get dirty every day you tow. Just deal with it.
5.Eventually you'll need a new windshield in the toad from pitting.