I have a black truck and I live in texas and I don't have shade, this is what i do. Like some one said before wash the truck in sections and keep spraying the rest of the truck down with water after each section to make sure the entire thing stays wet. Oh if your like me that has "car washing towels" when you wash them in your washing machine don't use fabric softener, dry them with out it, it helps with the streaking. Old painters trick....

 

What about "permanent" waterspots on chrome. I got them all over my front passenger side bumper.

 

Hmm have you tried Mothers Chrome wheel polish that may take the acidic water spots off.

I love my California Jelly Blade no more water spots...