You can use oil flo or something like LA Awesome found in dollar stores. A citrus will dissolve the adhesive too.
I have found that one of those, paired with bronze wool works good.
P.S. I HATE when they leave the film on too long. It’s a PITA to clean up. I had one house two years ago that had the film left on for three months, baking in the sun. You could have played Spiderman on those windows, they were so sticky.