Article: Set up your compressed air auto paint sprayer and add your chosen corrosion-resistant, self-etching automotive primer, all according to the product instructions. Hold the sprayer about 6 in (15 cm) from your practice surface, squeeze the trigger, and use a steady, side-to-side motion to coat the surface. Always maintain this sweeping motion while spraying.  A scrap car door from a local junkyard is the best practice material. However, a sheet of scrap steel will also do the job. A sheet of scrap wood or even cardboard is OK if necessary, but the primer and paint won’t spread and adhere in the same fashion. The process of loading and using a sprayer varies widely based on the brand and model. Follow the product instructions carefully. Make sure to put on all your safety gear first! Once you’ve mastered your spraying technique on your scrap material, replicate it on the vehicle. Aim to lay on a thin, even coat, starting at the roof and working down from there. Keep using the sweeping, side-to-side spraying motion throughout. It should take about 10-20 minutes to add a full primer coat to a typical vehicle. Follow the instructions on the container for letting the primer cure. The typical waiting time is 20-60 minutes. After that, repeat the process 1-2 more times, based on the product instructions.  After 2-3 coats of primer, the bare metal surface should be fully and evenly covered. Once you’re done applying primer, clean the sprayer according to the product instructions. Wait at least 1 hour after applying your last coat of primer, then use 1500-grit wet/dry sandpaper to smooth out the primed surfaces of the vehicle. Work section-by-section, sanding lightly from side-to-side, then up-and-down.  Some vehicle painters prefer to use sandpaper with an even finer grit, such as 2000-grit, for this task. It will take longer to do the job, but you’ll be less likely to sand off too much. Remember that your goal is just to remove the powdery finish, not to expose the bare metal beneath the primer. Use clean rags slightly dampened with a wax and grease remover, acetone, or paint thinner. Wipe fairly gently in circular motions, just enough to remove any accumulated dust or oil. Give the vehicle at least 5-10 minutes to dry before proceeding.

What is a summary?
Practice your spraying technique on a scrap car door or sheet metal. Apply a primer coat, working from the top of the car downward. Let the primer cure, then add 1-2 more coats as recommended for the product. Sand away the powdery finish of the primer coats with wet/dry sandpaper. Wipe down all primed and sanded surfaces before applying paint.