I have a door from an extended cab truck on my single cab. (busted up the original door pretty bad! LOL!)
anyhow, it had that black film on it... what you need to do is go to a body shop supply shop, like English Color or the like and get a pinstripe removal wheel... or "eraser wheel"... chuck it up in your drill and go to town. it won't damage the paint, but it takes the film off perfectly. While I was at it, I went ahead and debadged the truck. popped the badges off by hand and used the eraser wheel to remove the left over adhesive.
they work awesome.
Forrest