I see you already mentioned they already used dry wool. At the dealer where I worked we used really fine steel wool following a good spray of window cleaner. If that doesn't get it off whatever it is pretty much nothing will. But I'm betting the body shop probably already tried that.
Yes.
0000 (that's 4 zeros) steel wool. Very fine.
I did the outside of my windows to get little bits of debris and some water spots off the surface. I did it wet using the car wash soap I had in the bucket, but any cleaner/soap should work for light lubrication.
If you have aftermarket window film tint on the inside of the windows, proceed with caution. Not sure if the steel wool will scratch that film.