Fast and easy
If you haven't tried CC550, don't wait any longer! I use a separate smaller bucket and a 6" strip washer. I wear Nitrile gloves (cheap protection) and pour just a little bit of the CC550 into the bottom of the bucket and then dip the wand into that and apply to the glass. Apply it like you are going to wash the window but keep rubbing the glass with the wet CC550 wand until you feel that it is getting easier and easier to glide the wand over the glass. If necessary, while still wet I then clean the glass with fine steel wool. My preference is to only work on a portion of glass - in the shade and out of direct sunlight - and not let the CC550 dry on the pane of glass. Note, this is a very strong chemical! If you use steel wool you will notice that it will rust quickly. On the 6" washer wand, use a plastic one - I cut down an unger wand base to fit a 6" wand cover. I had an aluminum or steel one that I had used previously without rinsing after use and the remaining CC550 literally disintegrated the metal part of the wand. Also, if the glass is beyond recovery, it can leave the glass looking worse to the point where the client will almost certainly need to replace the glass - so make sure to explain that before starting, and get a signed damage release waver before even doing a test spot. If CC550 doesn't get the window completely clean, I then use Pulex Rub Off with an orbital sander and a Bonnet. You can read what I use under my review of Rub Off.