Best way to separate pinch welds

Also as said if you drill thru both sides you can weld up the holes. Use a copper block to the back side so it won't stick. I've used a body dolly for this as the dolly doesn't heat up enough to stick, as it cools off you can wiggle it free. I have also used a coat hanger. You bend it say 1/4" at a 90' angle and hold it over the hole and weld it. With a little practice it's easy to get the hang of it. Then wiggle it back and forth and snap it off and repeat