I used to have a clay bar that you would wet and rub into the glass or paint to remove spots and blemishes.

IIRC it was a zymol product. Worked great for the hard water spots in SoCal...don't need it in the PNW

 

Works great as long as it's water deposits that are making the spots.
I also use distilled water in the washer resevior, It's only minor but it if you have hard water in your area, tap water will leave more spots than it cleans.

 

I have used sparkle sold in Ace hardware stores for many years. sometime if the water spots are old it takes a couple of application.

Labarn