The paint needs to be thin enough to still let the wood vibrate. The more paint you apply, to more you kill frequencies in the sound and the guitar will sound dull.
If you feel confident in your abilities, you could carefully mask off all areas you don't want to paint, and then give it a rub with very fine sandpaper (800-1000 grain) in order to prepare the surface, and then apply the colour with a spray can, in several very thin layers. You should spray once (very thin!), let it set 30 mins, repeat. Then, let it dry thoroughly, we're talking almost a week here. Then, repeat the process until coverage is good enough. Then, snad the surface again (1000 grain) and repeat the same process with clearcoat spray. In the end, you need to sand the clearcoat with very very fine paper (2000 grain wetsanding) This will dull the clearcoat, but it is essential because you will want to apply polish. Car polish is ideal. Apply it in several coats , buffing and shining up the surface with thorough, circular motions.
Well, the process I described usually is used for electric guitars, but I don't see why it shouldn't apply to accoustics. At least I believe that spraypainting leaves thinner coats of colour than applying clour with a brush or something. It's a delicate process nonetheless, and don't take my guarantee that it will work.
Just trying to give you ideas about the process. Hope it helps...
