Me personally, I begin with a photo and from there, it's a bunch of different ways to do it depending on the contest, the photo toons were a kinda plaything since I'm a photographer I have access to my large format pictures, the bigger they are the better. I moved on to drawing out the car and simply painting it, all the stuff I use is basic photoshop tools that are in any of the programs. I mainly had to learn layers and that was it, once you learn layers, you're good to go, knowing when to flatten them or when to merge them. All the neat photoshop stuff like brushes and gradients are readliy available anywhere on the net for free I may add. I've taught guys within an hour to create something cool and give them a head start.
The more advanced guys know the pen tool, which I just can't seem to get right, i have two versions of photoshop on my comp and both pen tools work different.