The bare wood surface will act much like a sponge when your paint is first applied and it will take several coats of paint to seal and finish the wood. A better approach is to apply a wood sanding sealer to the wood. This acts like a primer coat for the wood and provides a good base to apply the colour finish paint.
Prepare a place to paint your car that will be out of the house while you are painting and out of the reach of young children while your car is drying. You may either paint one side at a time waiting between coats or suspend the car on a string with a nail in the axle slot and paint all of it. Brush or spray the sanding sealer on the car with a complete coat and wait for it to thoroughly dry. After it is dry, sand it with 400 grit wet or dry sandpaper. You will find that the finish is smoother if you use a wet-sanding process. Sand until the sanding-sealer is smooth but not through the sealer to the wood.
You are now ready for the finish colour coats of paint. The best and smoothest finishes will be had with a spray paint but brush-on paint will not effect the overall speed of the car either. Use fast drying enamels and avoid using different brands on top of each other. Above all don't use lacquer paint on top of enamel paint. Your paint will wrinkle and bubble. If you get a run in the paint, let it dry and sand it smooth. Re-coat it later. You can achieve a very, very smooth finish if you wet-sand between coats with 600 grit wet-or-dry sandpaper.
If you are going to apply decals and detail work now is time to do this type of work. If you are careful, you can apply a clear coat of finish over the decals to seal them. Don’t use too much clear-coat at a time or you’ll wrinkle the decals.