Painting windows with UV film
I want to paint 6-over-6 double hung windows to which, several years ago, we added UV film (DIY project that involved shampoo, but no adhesive). Can I do this without damaging the film on the glass? My usual method of painting is to paint the frame and muntins as carefully as possible and later use a razor blade to remove any paint on the glass. The alternative of using some kind of masking tape or painter's tape would seem also likely to tear the film. I hope the answer isn't to try some kind of paint shield: for me that is always just a tool to guarantee getting paint where I don't want it and making a bigger mess than if I did nothing at all but paint carefully!
Any ideas or instructions how to use a paint shield (if I need to)?
M in NJ