There are many types of spray paint. Some RC body painters recommend only using paint developed specifically for use on Lexan or other polycarbonate plastic used to make RC bodies. Others have good results with any old off-the-shelf spray paint or other paints such as automotive paint. Your first time out, you should probably stick with spray paints for RC bodies, such as Tamiya Polycarbonate Spray Paints or Pactra Polycarb Spray Paints.
Scuff the Painting SurfaceWhile not a step that everyone uses, when using spray paint -- especially paint not specifically formulated for use on Lexan RC bodies -- it can often help it adhere better if you scuff up the body a little. Use very fine sandpaper or steel wool to lightly scratch the surface of the body where it will be painted. Scuff lightly. Paint will hide light scratches but deep gouging will show. Don't do this to areas, such as windows, that won't be painted -- the scratches will show.
Shake the CanFollow the directions on the paint can and shake thoroughly before you begin painting.
Warm Up the PaintHold the can under warm running water or place the bottom in a bowl of warm water. The paint flows better when it's at 70 degrees or more. It will be thinner and spray more evenly. Use warm, not hot or boiling water. You want to warm it up, not overheat it. I've seen some people recommend putting the spray can in boiling water -- don't do this! Overheating the can could cause it to explode.
Do a Test SprayStart spraying away from the car body (onto cardboard or other paper) to avoid any sudden spurts and splatters from the can and to make sure you're applying the right amount of pressure. Then move toward the car body and spray your first layer.
Spray Light LayersDon't try to cover the surface solidly in one coat. Spray a very light, thin coat. It will be a fine, see-through misting. Let it dry. Add another light coat. Dry again. Do this as many times as it takes to build up to the complete coverage you want.
Three or four thin coats are better than one or two thick coats of paint -- less chance of bleeding under the masked areas and less chance of paint chipping or flaking or running. Some RC body painters recommend building up that first paint color in even thinner layers -- 5 or more. Later layers can be a bit thicker.
Don't Empty the Can
It may seem wasteful, but don't try to get every last drop of paint out of the spray can. Those last few sprays tend to come out in uneven spurts that can glob up or run and ruin your paint job before you've even finished.
However, you can use that last bit of paint in another way. After the paint on the body has dried completely, if you see some small spots that could use a touch-up, spray that last bit of paint in the can into a small container and use a brush to very carefully touch up any spots you missed. Don't try this before the sprayed on paint has dried or you'll end up with a big mess.
Let It DryThis is true for whatever kind of painting you do, spray cans, airbrush, brush. Let the finished paint job dry undisturbed for at least 24 hours or longer before handling, doing detailing, etc.
You could speed up the drying process by using a handheld blow dryer. Keep it on low to medium heat, not high blasting heat, and hold it at least a foot or so from the body moving it around slowly. Don't use the blow dryer on paint that has just been applied and is still liquid -- you may get runs. Wait for it to set up just a bit before using the dryer. You'll still want to wait before handling the body but the paint won't be tacky wet on the outside.