Welding ground...don't do this!

Uh, no............

The current that goes through you is what kills you but it is DRIVEN by voltage. And "most welders" are not necessarily 20V, either. My mig on higher settings is something above 40 or so, and many stick welders are up around 80V or so open circuit.
I just got hit with 370 volts, capacitor. Made my shoulder and elbow feel much better now (been hurting for a year after my fall)