Carl, I take off bondo with a hard wire wheel. Quick. I have a mask and a fan to blow away dust from the area.
If you pull a dent out, you may pull past flush and then have to hammer and dolly back. If you can't get behind, you can't do that. Can't control a slide hammer and it may bring dent out too far. Rethink a way to get access. I don't know what the area looks like. Maybe cut out the piece, hammer/dolly on the bench and weld back in. I'm sure there are some actual body men on here to advise. Check out "studlever" videos. Neat tool and allows better control than a slide hammer. Seems easy to make one.
