Hair dryer might have a spazz if you leave it on for too long. Best to find a proper hot air gun and use that on a medium low temperature to loosen the film and gently peel it away. After removal, use IPA to remove any adhesive remaining on the vehicle and wash.
If you are re-applying new film, cut and polish the area first before re-application, otherwise you might suffer from poor results further down the line when it starts to peel and bubble.
EDIT: You can pick up a special squeegee with a soft edge from the paint/sign shop. It won't scratch the surface like a credit card might. otherwise, you can line it with a couple of pieces of paper or thin cloth.