there are MATs you can download, place in your runtime, and just apply them to materials zones with one click.

if you do a search here, there were some car paint shaders posted that are really well done. be warned that you will take a bit of a rendertime hit. also, in order to do one of those showroom style car renders you need to create a white box above the vehicle to be reflected in the paint - but IIRC this was also covered in the car paint thread.

i would search for it for you but im really bandwidth challenged at the moment - my bandwidth cap rolls over tomorrow: i only had 2 gigs of mobile broadband to ration for a whole month :(

cheers