The best way is to get paint shop pro, some templates (I think they are still on RSC's forum, in the skins section), and just draw. Getting the basic colours right, and in the right places is the first thing. Once that's done, add the logos.
www.brandsoftheworld.com has a good selection of logos.
It's best to work with layers, that way you can easily adjust the skin, rather than ruin it in one accidental spurt. PNG files and PSPimage files I find are best.