This was done for the project "Guadalupe". It was the first time I tried something so challenging.
The car, hired only for a couple of hours, was shot standing still against a greenscreen.
A 3D model of the car was done in 3D Studio Max (the car paint is quite difficult to emulate). The model was surrounded by moving textures (taken from google images), so the car reflected the environment in order to add the sense of movement. The original reflections on the car were painted out by hand in Shake, to get rid of the camera and the surroinding production staff. The camera position relative to the car was estimated from the shots, and no tracking software was used.
Compositing was accomplished inside Combustion 4 and Shake on a Mac Intel. In some shots, some color grading and environmental effects were added, such as rain. The background footage had to be retimed and smoothed, and a lot of tweeking was necesary for the integration (although I´m not fully satisfied with the final result).