I just came out of my garage after removing 50+- trim screws from my 41 gmc door panels. As every one has experienced this can be a real b----. my solution was to take care of the easy ones then to switct to heat. Get your heat gun and set it right on the screw for 2-4 minutes then quickly put your screw driver into the slot and really pound it and then start breaking with forward and then reverse direction. What is happening is that you are burning rust with the heat and also making a new seat for the rusted heads of the screw. Try it, it works and you do not need "blaster" but you probably won't use the screws again either. It is a little slow but you will not be drilling out old screws. If it doesn't work the first time just turn up the heat and repeat. doug