How do big companies can products at large scales?
What I've seen (on TV, not in person) is typically somewhat different than a home process - the food is sealed in the cans (raw) and then run through a giant pressure cooker, typically on some sort of conveyor system, and spends a number of hours being cooked in the cans at the same time as it's being "canned" (heat-processed to kill bacteria) - at least this seems to apply to canned beans. Labels are applied after the can has cooled.