Since I restart some attempts to get a realistic car paint shader, I searched over the net. And I've found rather interesting articles.
Both are from Matt Ebb, you can show his site at http://mke3.net/.
The first one is using the plain old material system (that is, no nodes). It use a standard shader with large diffuse area and a specular ramp to add small high specular spots on the large diffuse area. Here's his post about it.
The second is using the 2.42-added node system. Here's an introduction about it (also mentionning Matt Bet's work). He posted here about it.
In the next few days I will be experimentating with both moves. The second is very impressive, but imcompatible with Yafray. So I've either to play with Blender renderer (and Ambient Occlusion settings), or to use the first method in Yafray.
So some new renders of the DB9 will be posted soon !