well at least your filler is at the edges where it's tight and won't affect the middle as much. I'd block on the metal like this //// with 80 grit and then get a good look at what you got going. You can also use a sharpy and make a little grid as your guide coat, or just use the scratches in the metal. Then you can push up on your lows while tapping down on the adjacent highs. You can also hammer from below and push from above. Once you got all the areas then take a flat tear drop mallet/ finishing hammer and dolly/ shot bag and smooth it out. You can also smooth it out from both sides. Then guide coat like this \\\ which is the opposite direction from the last scratches you left which makes it easier to identify. Then repeat til it's straight and more stiff.
Roofs are a pain but when you have access to both sides it just takes a little more time to get it right and it's worth it cause you not only leave yourself with less dust in your garage but you give it the proper flex back. Shrinking disks work well with roofs to finish off.
Last edited by tech69; 04-28-2011 at 11:37 PM.