Spray painting a car is a job that is best left to professionals, as he or she will have the tools that are needed to get the job done right, and will also know how to protect themselves from the fumes and chemicals that are in paint. However, if you do want to try to tackle this work on your own, note a few common problems and mistakes that you'll want to avoid, so the job comes out looking its best.
Running or sagging
If the paint begins to run or sag as it dries, this is often caused by an improper painting technique. It's important to use the right nozzle on the spray paint can and the right pressure when applying the paint, and to ensure you're holding the nozzle so that it's aimed directly at the vehicle's surface. If you were to tilt the can or apply too much pressure, this can cause thick paint in some areas that is then prone to running or sagging, which you may not notice until the paint begins to dry. Practice on some pieces of plywood or other such surfaces until you're accustomed to holding the can properly before painting your vehicle.
Flaking and peeling
If a car's paint begins to flake or peel off after it's been applied, this often means the surface was not prepared properly. As with any other material, a car's frame may need some sanding in order to create texture that will hold the paint. Also, you need to ensure you're using the right type of paint for the car's body, as standard epoxies and other such types of exterior paints won't adhere properly to a car's frame. Only opt for paint meant for metal, to ensure it avoids flaking or even outright peeling off once it's applied.
Orange peel finish
An orange peel finish refers to small dots or bubbles that appear along the entire surface of the paint after it's applied. These dots are often caused by paint that is too thick; the paint may not run or sag, as mentioned above, but it cannot settle onto the vehicle's surface evenly and offer a smooth finish. When you use a paint sprayer, you typically need to prepare the paint with a reducer. Not using enough reducer in the paint can cause it to stay very thick, and it then bubbles and creates this bumpy texture. Be sure you note how much reducer is needed for your car's material so that the paint doesn't become overly thick this way.