"My friend was trying to create a protected sub circuit in a garage, where there was no access to the breaker, because it was in the house. I instructed him to install a sub panel with breakers and GFCIs in the outlets -- or use GFCI breakers. An expensive option. "

Not all that bad really, unless you don't know where to get the stuff. I little 6 position MLO might only be $ 30, one 240 V GFCI, that's expensive. thing is, if there was no wiring in the garage before, they want to see arc proof. Whether that is actually law is debatable, but the GFCI breakers can be as low as like $ 15. (regular breakers are inder $ 10) so 3 of them and one 240, that meets the requirement of five moves or less to shut down the building. (but not if it is an attached garage, then you got no problems as long as there is a main breaker at the mains coming in, if you run separate SERVICE that is different and I have known people to do that, they painted cars and had a huge compressor)