[dsraven]

have you thought of trying a shrinking disc or a shrinking method like that? I have heard that some have used a laundry iron set to very hot as well. basically the flat hot thing heats up the high spots, not too much-just enough to cause some steam when you cool it with a wet rag, and that shrinks just the high spots down o be more level with the low spots. I have a small and large disc set from Wray Schelen (?) and have used them a bunch on my rear fenders. they were bad but after a bunch of hammer and dolly work they came out pretty smooth after the disc work. no filler used, just some high build primer, sand, etc.
if you haven't already tried it, a big fat tip marker from the dollar store works pretty well to show high spots. rub the marker all over the area, then when you use a flat sanding board (I use a piece of 3/4 plywood with a sanding strip stapled on because it doen't bend like the plastic boards do) the board sands off the high spots and shows the low spots where the marker hasn't been sanded off yet. then use a flat faced hammer and a dolly that is shaped close to the shape you need to massage out the hogh spots and/or bring up the low spots to flatten out the area and if it ends up lookinh like a bubble then shrink disc the whole area to take the bubble out. I also use a slapper made from a truck spring as a hammer sometimes because it is way wider than a hammer face for some of the larger areas.
worked for me.
keep plugging away and soon you will be done. turn the shop lights off after and use a bright light on the inside of the area so you can detect any pin holes.