For car paint touch up first, you need to use a good brush, not the garbage that comes in a touch-up paint bottle. Get an artist's mink or sable brush. Cut it at a 45 degree angle. Daub it on - do not brush it - as you go. Let the paint slide down the bristles and into the scratch / chip. Clear off excess paint from the brush first. the basic idea behind this Car paint tutorial is to mix 2 layers, one will only add strong and quite sharp reflections and spectaculars + another which will give the color + very spread and dim reflections, now to accomplish this i will avoid the creation of a maya layer shade, it could be done though, but you have to mask transparency values which slow renders quite a lot. I m gonna use a different approach, under the mix8layer options we have tons of cool and nice blending techniques to blend different shades, most of them are quite common to Photoshop users, Anyone for a SCREEN blending? The principle is this: Nacar shade will have a BLACK diffuse color and very sharp reflections in it, this shade will go as a layer on top of the color shade. Color shade will have the color we want to paint the car with applied to the diffuse channel, so if we want green car, just select this color in the diffuse.(Of course, if you want an image as color just put it!!) now, the reflections of this color shade will be very blurry , spread and soft .Color shade will be the base or background layer, by blending the Nacar layer in SCREEN mode on top we will be adding only the reflections, because the diffusion is black.