Quality control is the ongoing review of work as the project moves along, checking coverage, lines, and finish quality at each step. Catching an issue while the crew is still on site is what turns a good paint job into one we stand behind.
The final walkthrough is the formal check, but the real work happens during the job. Coats are inspected as they go down, not just at the end, because correcting a coat early costs minutes rather than requiring a full rework.