Unless it's a towbarless tug in which case only two are required, driver and headset.
In your neck of the woods. Where I am, however, it's all done by a single person. Head-set is of the bluetooth variety, so no cords to contend with. If we're using a tow bar, it's a two-man job. But we only use tow bars as a last resort back-up.
During my time in the business, 9 times out of 10 when a push-back has gone wrong, it's the flight-deck who's been ahead of themselves. That's the main reason a chock is placed in front of the nose wheel before disconnecting tow bar; to minimise the risk of getting run over by a crew, who releases the brakes without clear signal from the ground. Have seen that happen too many times to remember. Funny thing is, when it happens the airline always have a phalanx of excuses, and as good as never revises any procedures as a consequence. But if the handling agent gets it wrong just once, perhaps snapping a shear pin, the airlines want blood, procedure revisions, updated risk assessments, read & signs, staff briefings and what not. We once had an incident just like that, and was hammered by the airline from Atlanta. The very next day, skipper released brakes and the operator on the ground was only saved by the nose chock. I naturally turned the tables and requested the same from Atlanta, as Atlanta did from us. It all got very, very silent after that. Probably around a year ago now, still haven't heard from them.