Not an expert here, but I have done my share of bondo removal and pounding metal. Most of the time if you have access to the back side of the dent you can tap it first. This will release some of the bondo making it easier to remove.
After the initial pounding, I use strip-it type disks for removal of everything including bondo. This allows you to go directly to the metal without destroying it. They are available on-line and swap meets too.
I am with you though, I don't understand why someone goes through all of the trouble to fix the dent with bondo, when with just a few minutes of hammer and dolly work you can have a near perfect surface and with experience you can have a perfect surface without bondo.
