What's the beast method/product to remove these "stains" of my door glasses? Vinegar? Rubbing compound? Windex and other glass cleaners won't touch it. Bottom picture is hard to see the dull spot, but the top picture shows it pretty well. The spot is smooth with no noticeable texture. Just a dull "stain". This particular window I got from a 2nd Gen collector with a bunch of parts cars. He had a stack of these door glasses inside one of his junk cars. I got the one with the least amount or scratches...but it has these stains.