i would hold the dolly in the mid part of the dent if smaller then the dolly the dolly as to have all most the same shape as the door now hold it up to the dent put pressure on the dolly and work the out side to the mid part of the dent do not beat the hell out of it you will not need to hit it to hard and look at it and see how it unlocks if done right it will come out if you work it out the right way when working with steel do not hit any harder then you have to or more then you have to .this is the best advise i can give you