If it's wavy it's probably stretched so pulling one depression is just going to move the excess metal somewhere else and you're going to wind up with an oil can situation.
Shrinking metal with a torch and water or compressed air is amazingly effective and very simple. I had only seen it done once about 35 years ago but still had great success with the rear of my cab which was caved in pretty bad from years of having cargo slammed against it because the front of the bed was missing.
PICTURE My biggest mistake was not trusting myself and having a bodyman friend finish the job. He had never shrunk metal and just mudded it over. Although it came out well, I'm sure a couple more well-placed shrinks could have gotten it MUCH better.
Good luck!
