For minor dents, the Dent King would be a great tool. Or, if you can get BEHIND the dented panel, get a metal rod, or sort of rod that won't break or bend...and a couple soft rags..

Start at the outer edges of the dent and gently 'massage' them out, working from the out edges until it's gone. Take the rod and put the soft rags behind your dent, and use the rod to massage the edges out. 

It's not guarentee'd to fully remove the dent, but that's what filler is for and you just might be up a creek without a paddle after that ;)