Clean the surface of your vehicle to ensure proper adhesion of the paint. Wash the automobile with car wash soap and water. Once dry, wipe the car down with an automotive wax and grease remover.
Wet-sand the areas to be painted with 600-grit wet/dry sandpaper. Start by soaking the sand paper in a bucket of water --- 3 to 5 drops of dish washing soap added. Place the sandpaper on a sanding block or an electric sander.
Wipe the car with an automotive pre-paint cleaner. This will mildly etch the surface, as well as remove all sanding residue.
Cover all areas not to be painted, such as the windows, wheels and grill with masking paper and tape. Cover the areas to be painted with self-adhesive masking film.
Reference images of flames online, at AutoGraphicDecals.com and SignSpecialist.com. Or in a hot rod magazines such as Truckin' Magazine.
Draw your flame design onto the masking film using a permanent marker.
Trace around the flame shapes with a craft knife.
Peel away the flame shapes, leaving the space around the flames still masked.
Paint the flame areas with automotive primer, using a paint sprayer. Apply three coats of primer. Allow the final coat of primer to completely dry. Primer should be dry within 45 minutes.
Use a paint sprayer to paint the flames. For gradations of more than one color, apply the light color, then add darker colors. Overlap and feather the edges to create smooth transitions. Feather an edge by spraying light, wispy sprays of one color where it overlaps the previous color. This will make some of the lighter color show through the darker color, creating a gradual, rather than abrupt, change from one color to the next.
Remove the rest of the self-adhesive masking paper before the paint dries, otherwise the masking paper can lift the paint with it. You can check dryness by touching paint on the masking paper (so you do not get fingerprints on the car). Remove masking paper when the paint feels slightly tacky.
Create a graphic outline around the flames with black, or with a color that goes well with the flame color. Carefully hand-paint the graphic outlines using a thin, round paintbrush, such as a size 2 or 4 brush. Allow the paint job to dry for 24 hours.
Spray the automobile with 3 coats of automotive clear coat to bring back the luster and shine. Spray the clear coat consistently over the flame areas and outside the flame areas. Allow the clear coat to dry according to the dry time on the can.
Remove the masking from unpainted areas.
Buff the car with a soft cloth and automotive wax for a final, protective coating.