Honestly thought that whole tape thing was just for show until a buddy got me to try it on a local river dive. Got completely turned around in some thick silt and that bright pink line was the only thing I could see. Now I won't go into low vis without it, cheap insurance. The trick is getting the good vinyl stuff that doesn't peel off.

Honestly that's a solid trick for thin sheet metal. Tbh a 3/8" panel is pretty thick though, you sure it wasn't gauge steel? That suction cup method usually needs something thinner to get a real grip. Still, getting a dent out with the wrong tool always feels like a win.

That "damp cheesecloth" idea would make me worry about raising the grain.

Seriously, that just makes them find a cheaper freelancer next time.

Grab a can of compressed air keyboard cleaner and turn it upside down to freeze the bolt. Works way better than just waiting for a cold day. Just watch your fingers because that stuff gets seriously cold. I've had to do that more than once on old aluminum intake manifolds.