Thanks Brad Wardell for emailing us ;)
Stardock has finally released a comprehensive skinning guide.
It provides a web based guide to everything from describing the various elements of a GUI and how they are skinned to tips and tricks on how to make your skins faster.
The guide includes a link to a seperate Adobe Acrobat file that includes full documentation of the WindowBlinds skinning language with examples on how to create simple skins (less than a page of code) to advanced animation techniques.
View: Skinning Guide
Screenshot: Windows Blind Desktop