White spirit.
hairdryer can melt the paint also.
Start at the top of the PF while its still in the game and on an incline, put some white spirit under the lip of the mylar and pull back slightly.. it will just lift off with no effort. Then apply again etc all the way down the PF.
Plenty of residue will be left and will need elbow grease and a cloth to remove, but white spirit will seperate the glue from the plastic sheeting
To confirm this, you are just using white spirit and nothing else. No hairdryer as your worried it will melt the paint.
I use nothing but White Spirit and have lifted mylar from some very shakey paint with this method.
If you heat the mylar to the point that the glue goes soft then you are also heating the paint and hoping that the paint still adheres to the PF better than the heated mylar. I havent used a hair dryer for a long time