I hope this is helpful! I received many requests for tutorials but putting together a full tutorial will take a lot of time. This is not a complete step-by-step process, but it covers my general process. This tutorial assumes you know the basics of photoshop. If you are unsure of where anything is, try it out in PS or use google for help. I know it can seem complex and confusing at first, but you'll get the hang of it! Best of luck!

Great Brush Packs:

http://tazihound.deviantart.com/art/Shading-Tutorial-579006347