I personally attempt the heat method first in use a hair dryer which isn't hot enough to melt the paint so if the glue doesn't melt with this method I use the white spirit.   Once the Mylar is removed I use white spirit on the glue I've had zero problems with the white spirit affecting paint of Playfields from 50s to 90s machines



   The freeze spray would work on the 90s games as the paint has a better bond to the Playfield and the clear coat locks everything in the older games your literally removing Mylar from your artwork and its scary no matter how many times you have done it