I can definitely be of assistance. I own California Sunscreen Window Tinting in San Leandro, CA Bay Area and have been tinting for over 14 years.
Tint removal is actually harder than tinting itself. There are so many different types of window film and different formula of adhesives that it is really difficult to determine. If it is a side window, you can just pick at a corner and peel it off like a sticker. Usually the trick is to put a little heat on it to soften the glue and pull very slowly so that you can try and keep all the adhesive to the film instead of pulling hard and fast and leaving all the glue on the glass. After you remove the film, you will need to use soap water solution and spray it on the glue. Use a FRESH/CLEAN razor blade and slowly scrape it off using up and down motion. Do not scrape sideways as the edges of the razor blade may scratch the glass. Make sure the area you are scraping is well lubricated with soap water so the glue does not smear.
Now for the back window, it is a totally different animal. If you can remove the film to expose the glue, you can clean that off with _____. It is kind of a trade secret but if you e-mail me, I will let you know. Using a garbage bag trick works sometime but not all the time. If the old tint is bubbled up and is all purple, that is usually the worst scenario. The film is constructed in multiple layers. Sometimes when you start peeling off the film, you think you got it all off but actually you left the second layer on. That will make things a nightmare. If you are lucky, all the glue will come off with the film while you are peeling it off. Please describe in detail the condition of the tint. Is it bubbled up, distorted, etc.? The other tool that we use is a steamer. We actually steam off the tint to expose the glue and then we use the secret _______ to remove the glue. If we remove tint from rear windows, we usually charge between $75-$150 just for the back window with defrost lines. The sides are only $15 per roll up, $10 per quarter and $5 per vent.
Make sure you do not use a razor blade when removing tint off the rear window with defrost lines as it is very easy to scrape the defrost line and break it, rendering it useless for that particular line.
If you have any more questions, please don't hesitate to ask. Good luck. It is not easy at all!
Sidney Lee
California Sunscreen
(510)483-8468