Since the car is mostly composed of shaders and a few textures, I spent most of the time tweaking Maya's mental ray shaders. For the car paint, I used the mi_car_paint_phen shader and I did many test renders to get it just how I wanted it (Fig.05). The best way to use this shader is to make little changes as you do test renders. If I liked one particular configuration, I would duplicate the shader several times and keep on testing these duplicates, so that I would always have the original still in case I wanted to go back to it.
As for the wheel rims, windows, lights or basically anything with any kind of reflection or refraction, I used the mia_material_x shader. Once you know what the values mean, it can be tweaked to a variety of materials, like glass, plastic, metals, etc., and it has the advantage of coming with a bunch of presets in case you don't know where to start (Fig.06).
My focus then became the lighting of the car, which in the beginning was my main goal for reworking the car. After seeing lots of beautiful car renderings, I found out that they were based on real-life studio lighting setups (Fig.07). As you can see, these setups are all different from each other, with all types of lights and backgrounds. So there is no "golden setup" that can be used for every render you make.
After a bunch of research on the internet, reading 3D car forums and tutorials, and lots of experimenting with area lights, light cards, and HDRI studio images in Maya, I decided to take a simpler approach by using a black and white gradient to light the scene. This method was suggested in a couple of forums, and the result was satisfactory. So in the end, I used a gradient and a soft spotlight on top of the car to light the car (Fig.08). Sometimes less is more!
In order to set up the gradient, you have to open the Render Settings window. Go to the Indirect Lighting (make sure mental ray is the current renderer) and click on Create on Image Based Lighting under the Environment rollout
After that, change the Type to Texture and create a Ramp. The most important part is setting the V value for the white part of the gradient above 1 so that it has the strength to light the scene (Fig.10).
As far as the spotlight goes, it is set far away from the car in order to get almost parallel rays (as it is with a directional light), with a low intensity and soft raytraced shadows (Fig.11).