I used to work with an old school radio engineer who used his fingers to test circuits. He knew the capacitance of each of his fingers, both wet and dry.
when we bought Triple S they had some old shit in there, one was a stick welder the side a of V8 engine, the cables had to be undone and moved to change amps, it had a had a bit of 8mm microbore copper pipe in the plug as a fuse.