I'm terribly sorry to dig up an old thread but I wanted to add my bit into this.
Not true. While this method can be used (firing single flash on each section of the car, then creating seperate layers and revealing each shots highlights and another seperate layer(s) for sky, etc) is possible, it would not make sense that these photos would be taken using that method as it is at dusk/night and the softness of the sky and slight motion blur on trees suggest these photos are produced by using a long exposure + a flash that is fired multiple times over the exposure. This is essentially called 'light painting', and is a common used practice for automotive photography because you can get full coverage of the car with 1 flash with good batteries where as you would need ~4 remote flashes to cover it otherwise, plus it gives it a great efffect. I personally, choose the method of 3 strobes so i can get a nice balanced light during the middle of the day or other times where there is a lot of ambient light.
Filter, not necessarily, depending what time of day this was shot at (just after dusk), the long exposure can picj up a lot of light that is not evident to the naked eye, an orange tinge becomes apparent with a recently set sun/surrounding lights.
As far as photoshop goes, there was probably photoshop used for small things, which, ALL good photographers do, and i should make it very clear that ALL professional photographers extensivly use photoshop. Retouching, adjusting levels, colour, contrast, all of that kind of stuff. In terms of producing the picture to come out like it has, it would have all essentially been done on the camera, and photoshop retouches would just be a minor thing.
Try it sometime, you just need an SLR and a flash. Set your exposure to ~10" or longer as desires and equal out your ISO and F stop accordingly to acheive a balanced ambient light, then set your flash to full power and just press the fire button to paint areas of the car you want light on.
-Drew.