A friend of mine who does high end body work for a living and does amazing work had an AD come into the shop that had a tree fall on the roof and dented it way worse than yours.
He used a porta-power set to push the caved in roof back up. He moved it around several times to even out the process to avoid stretching the metal even worse that what the tree did. Once he roughed it out with the porta-power, he then proceeded with thousands of specifically controlled body hammer blows to bring it back into shape.
He said one thing that stuck with me. "That roof wants to go back into its original shape, I just had to help it get there."
There is another old saying that reminds me of the same principal. A local ancient decoy carver explained how to carve a duck out of a block of wood. He said with a wry smile, "You just need to remove everything that doesn't look like a duck."
