Hey Gang,
Picked up one of my doors from the blaster yesterday. When I bought my car, the driver's side door had a big dent...no big deal, I worked most of it out just for fun. In fact, the door looked salvagable. the car had been hit at some point in time and body work/paint was done. Well, this is what the blaster uncovered. This is NOT how you should do bodywork! Go out and buy, "The Key to Metal Bumping" by Frank Sargent and do it the right way!
For those not sure what you're looking at, in the bad days of body work, big dents and dings were pulled out by screwing in screws to the dent, attaching the screws to a slide hammer, and banging out the dent. The rough dent was then filled with lots of filler, including the screw holes. The best procedure is to actually bump the metal out from the backside using hammer and dolly techniques. In some cases, jacks would be used. It's actually quite easy to work a big dent out of a door, even if the door has a safety brace. You can get a set of sthingys used for just such purposes. Also, you can get air bags which can be sandwiched between the skin and inner structure and inflated to pop out the metal. For blind areas, a good bodyman will actually cut an access hole to facilitate metal working from the backside. This is commonly done with paintless ding repair. Many body shops use stud welders to attach studs which can be pulled on with slide hammers and pullers.
remember, the goal is to get the metal into shape so that 1/8" or less of filler is needed. You can usually do even better with just metal bumping!