I had '76 Ford pickup with the crispy, rock-hard window tint glue. I used a single edged razor blade and it took quite a while, but I got it off. Ammonia cleaned up the residue.
I'm sure it's possible, but I can't fathom an adhesive on glass that won't relent to a new, sharp single-edged razor blade, held at a narrow angle of incidence to the glass. Maybe a fairly aggressive scotchbrite pad would work, but you'd be risking scratching the glass with most of them. Maybe call a window-tint shop and ask what they use in worst-case scenarios?
Goof Off contains xylene, acetone, alcohols, and a mixture of various other solvents. This is why it works so well, but also why it eats into nearly any plastic on which it is spilled.
Steve H. - KE0KNH
Colo Springs, CO
'78 FJ40, '89 FJ62, '98 4Runner