I have a very big vise with which to do that. I put the trap in the vise upside down, and close the jaws of the vise until it compresses the jaws and lets them come free of the frame. But if the trap is badly bent, don't worry about it. Just force the jaw out as best you can. With the vice open wide, I rest the frame, at the hinge points, on the jaws of the vice, and with a heavy hammer, pound down the center of the frame. Bend and twist as necessary to return the trap to working conditions.
I've had a whole bunch of machinery vs trap experience.
Endeavor to persevere.