Spray the painted area with warm water, and wait 3 minutes. then remove it with a razor scraper. It so easy.no scratches at all on the glass. (experience: holiday painting on glass for 5 years )
Professional Window Painters Use "Outdoor Latex House Paint" The best brand is Sherwinn Williams - It's more expensive, but worth it! Miller is also very good. Tempra is not a good paint. It's weak....
I got flat, white spray paint overspray on the windshield of my car. Mind you, this was a simple, faint mist of overspray. You coulnd't see it, but when I used the wipers, I could tell it was there....