I have done this on several vehicles and I know this way works. This is not the best time of year because outside in the sun would help but start by soaking paper towels in amonia, get the lemon stuff because it helps with the odor, then stick them on the tint you want to remove. Get some plastic bags (grocery one's will work) and cut them so they will lay flat and stick them on the soaked paper towels on the windows. These will all stay stuck pretty good but if you need help around the edges use clothespins. Let this set at least an hour, the plastic will keep the moisture in, then use a razor blade and a little amonia and work it off, it usually will come off in one sheet. Even on tint that has been on +10 years.