If you can reach the spot the palm of the hand method might work fine, but you should consider the paintless dent removal services mentioned in some of the other posts. They repair stuff like you describe all day long.
I've used the Ding King, and it works like a champ. No drilling. Uses hot glue to affix a tab to the center of the dent, and a second screw handle tool to slowly pull the dent out. Ding King runs about 19.95 at the local Checker Auto, but requires a little practice to do it right on a larger dent.