Originally Posted by
gmwillys
A good heat gun will. Direct the heat to the valley of the ripple. You can also put ice water in a bucket, and use an old towel. When the metal is hot, wipe the towel over the valley. The metal will shrink. This is how most paintless dent repair shops fix hail dents.
Since you are still in bare metal, you can take a sanding disk, (paper backed) and flip it upside down in the DA sander. Run the back side on the metal to cause friction, but not remove material. Do this quickly, moving the grinder around, then let air cool. Watch the results, and apply more where needed.