The silicone adhesive actually parts from the door easily the next time. You don't slather it all over the thing, just make a bead paralleling the old mastic. Works great.

 

OK I am deep into doors right now fishing for window regulators. But here's my tip on removing the plastic film on the door frame under the door panel.

Tools to use:

1. Patience.
2. Patience.
3. Patience.
4. Close the doors, crank up the floor heat on your rig and let it idle baking the inside of the truck for a good half hour - the door film just peels off easily!!!! Actually the hotter the inside of the truck, the less you need of tools 1 - 3.

FordxFour Alternative: Do the job in the Summer. But I personally have less patience when working on vehicles outdoors in the Summer heat...

And forget about the heat gun alternative. Even on low heat, as predicted the gun heats the film - not the metal door frame - causing the film to tear, melt or stretch. I guess it can be done, but you will need alot more of tools 1 - 3.