Probably depends on the shop as well as the vehicle. In the old days we used to use the heater hoses to flush the entire system. Could flush it with a hose until it ran clear and then drain out a gallon from the radiator and fill it back with new antifreeze. I have the coolant flushed every few years in my daily drivers but I don't know how they do it. It seems to work since the fluid looks good after the flush but I've never watched them.