I have had pretty good success using a big spoon and pressure. Pick a really big spoon, stainless steel or plastic, and work on the inside of the dent. DON'T start on the high spot! Slide the spoon around the outside of the dent using the pressure of your thumb. It really helps if you can see the other side. Just keep working slowly and toward the high spot of the dent. I tried this the first time when my 70 pound Lab put a paw print in my rudder skin. Don't ask why it was on the livingroom carpet. The rudder was done except for closing the trailing edge. I can't even find it now. If the metal isn't streched, this seems to work, although your mileage may vary. A guy who makes his living repairing Cessna sheetmetal showed me this one.
Bob Kelly, 90854 painting
And yes, we still have the dog