As a self-educated car designer, I know too well how hard it is to imagine, sketch and render one’s ideas. I would like once again to share with you the process I’ve come up with to do this at a fairly good level.
First, sketching with a very broad pencil allows you to illustrate the essential idea. I used a single black marker to do the original sketch. It’s an early stage so this is not the time to be drawing into the details yet. It's a good way to learn how to keep a style that is sober, and to have control over the main features of the design proposal. It should come to you fast for it to really work. The sketch size should also be larger than a pencil drawing.
I decided to colorize a hotrod in a side view to show how dynamism can come from lighting (lens flare, sunny day, red lamp) and shadows. In the beginning, I always wonder what would be the best environment to set the car in to get the best out it. And that’s why I do lots, lots of trials before I finally choose one.
Here I imagined a futuristic hotrod that creases the concrete as, in my mind, the driver craves for adrenaline and enters the tunnel the wrong way. Smoke creates a certain atmosphere and adds realism to the scene.
I used Photoshop CS3, a Wacom Intuos3 A4 tablet...and loads of layers (215!). And most importantly, tons of masks.
see other tutorials here : http://www.behance.net/gamiette