This is the first iteration of my car paint toy box - so-called because it contains not just demo materials made from scratch but the node setups which are built from lower-level nodes as groups.
The materials presented are ready to use in Cycles and can be tuned to your needs from simply changing the base colour right through to changing the colour and presentation of the reflections. I'm developing this with artists in mind so the node interface is tailored in that direction.
Included are samples setups to generate a variety of paint finishes including bi-colour with funky specular highlights right down to steels, rust, primer coats and even "bodge" (body filler).
Also included (but not used in this example file) is a multi-shader mixer capable of mixing up to 10 different shaders at using a single image to map the effects to your model: this would allow you to create the effect of a car being prepared in a body shop after an accident or for re-painting after rust treatment.
V1.01 adds a new group for modulating the gloss effect to reduce the pure CGI look of high gloss. A sample of the effect applied to a painted surface is included under "red leather".
Sample images here include treatments from Robin Marin's cycles test scene as modified by Gottfried Hofmann.