Sorry about the late-ish reply, was having a few probs with my account.
If the ding is small enough, you may be able to "rub" it out, using an appropriate dolly. Select your dolly according to the shape of the panel that your working on. Obviously if its a flat panel you wouldn't use a dolly thats too curvatious.
From re-reading your post this would probably be the best option for you IMO. Try and be as gentle as you can be, and try and work it over a broard-ish area, but not too far, or you will end up with a big "high spot". Although i would consider this to be better than a great big ding in your tailgate or whatever.
So go and get yourself a Dolly or two, i think you can pick them up from Repco, or alike. Granted they're not awesome, top of the range dolly's, but they'll definatly do, its what i use.
I learnt all this doing a short TAFE course, in Geelong. It was only 3months, and like $600 ish. But definately worth it, hey i dont have to pay a panel beater to beat out what other people beat in