Hi a lot of old glass that has been painted can be cleaned off using super clean degreaser. I use mine straight strength get a tub and soak the part in the cleaner for awhile. when it starts to loosen up take a tooth brush and clean the part(do not allow the cleaner to dry on the part)and rinse it under warm water after cleaning. this will take the paint off, after cleaning you can polish the old glass with (kit scratch-out)automotive polish for real cars...It works very good just remember the plastic glass may be fragile so you dont break it. I have done this many times with great results....I am trying to restore my dads old models and it has worked on them as well.