A good job starts with proper preparation. A ventilation system needs to vent fumes to the outside. Don’t settle for anything less. In order to prevent spurious coating from getting on walls or other fixtures, the area should be thoroughly masked using tape and drop cloths.
Repairs include small cracks, dents, scratches, rust or burns. Yes, some people smoke in the tub!
The surface needs to be properly prepared so the coating permanently adheres. Skipped steps here can lead to a surface with pits, or worse yet, one that peels.
Finally the color coat is applied with a professional grade spray gun. Practice makes perfect with this step. If coating is applied too thick you can get streaks. If not enough is applied, the finish may not take hold properly.