They use robots to paint them and apply anti-fouling coatings. They also use loads and loads of automated machinery to create the steel parts that make up most of the ship. Do you think some dudes are forging rivets, beams, and pipes by hand? No, those are made by machines that make zillions of them.

The missing piece here is assembly, and disassembly is like 95% of what goes into recycling from what I understand.