The adhesive is usually called DA, standing for "Dry Adhesive". In effect, it is a chemical bonding with the glass and so much harder to remove than the PS type.
The best way to start, is the use of a packet of sharp razor blades. If your glass is not toughened, you should be ok. If it is toughened, you risk to scratch the glass in the process, so EXTREME CARE is needed.
Step 1: Wet the glass with a solution of soapy water and start scraping the film, preferably all layers at once. Keep re-wetting the film and glass, as you go. Change the blade frequently. Once you have removed all the film, go to
Step 2: Keep the glass wet, let it soak a while and go over the entire area again with the blade, until all the residue of adhesive has been removed.
Step 3: Again, glass wet, use a cleaning squeegee to remove all the loose adhesive and film residue. Finished!
Be careful during the whole process to not break the glass or cut yourself. The other thing to watch is to take care not damaging the rubber or paint on the frames.