14 If you plan on spraying in your garage, it's a good idea to hose off the rafters a couple days before. This will remove any dust on them, but make sure to give the area ample time to dry out. Then, coat the walls with plastic to create a makeshift booth. Another water tip is to wet the floor of the garage/booth right before you spray. The water will grab and hold onto overspray instead of letting it bounce back up and stick to the car.