Heh. I did something like that on a ride. Skidded sideways on some loose gravel and sand on freshly chipsealed pavement, warping the single wall rear rim. Spokes were probably too loose as well.
I braced the wheel against a utility pole and pushed from one side, pulled from the other, until it was straight enough to ride to the LBS.
At the shop the tech whanged the entire wheel against a heavy duty wooden bench. Tweaked a couple of spokes. Straightened it perfectly. And it held for two years before I was hit by a car on that bike, finally wrecking both wheels.
I knew some gunsmiths who used a similar technique to straighten rifle barrels, particularly with spring piston air rifles that use the barrel as a cocking lever. They'd detach the barrel (and any iron sights, etc.) and whap it like a whip against the wooden work bench until it was straight. The trick was to whap it flat against the bench. Worked remarkably well. But that probably wouldn't work with thin shotgun barrels.