They were using microfiber towels. My windows had spots that I could not removed with rubbing hard with a terry cloth towel. the spot were not so bad that I could feel them with my finger nail. I tried a small spot with a terry cloth towel and I could tell it would work. So I gave them the go ahead. You should be able to tell if it is going to work before the postman is down the street. I want to find the 303 shower shield to prevent this happening again.
Greg