I am sometimes asked how I work, and now I finally have something I can link to people. I am just one of many professional artists who have contributed game art tutorials to the new Vertex digital publication: www.artbypapercut.com/
My tutorial in particular (starting on page 118) covers diffuse painted models using my Avian Defender eagle character (fav.me/d4252y1) as an example. There's tons of great content in there spanning many game art disciplines. Best of all, it's a FREE download!
I have an early edit of the tutorial up on my web space as well: haikai.net/AvianDefender/
This may be easier to read with simplified formatting and larger images, but it's missing a few images that the published version has. Please comment if you have any questions.
* PS - I hope to be uploading a few more of my works from Guild Wars 2 soon!