Never wash in full sun especially when hot. Given the size of RVs two people work better, as getting it washed and rinsed and dried more quickly will help prevent spots and streaks.
The car washes that say spot free or reduced spotting work best. After washing top, wash and rinse and dry one side then do the other side, then the ends.
We use towels on long squeegie to dry. Wash early in the morning is the best, or late afternoon. Filter your rinse hose and the water you wash with. In decateu, Indiana the water is so bad the People that wash coaches for hire bring their own large supply of good water. The water there is s bad it looks like you sprayed salt on it anywhere the water settles. A filter may not get such bad mineralization. Dish water softener mixed in a bucket of water and wiping down the sides of splashed on it will eliminate streaks and spots.
