This still doesn't invalidate the fact that, after more than 10 years, Stardock has no excuse for not having detailed skinning tutorials and detailed skinning documentation available.
Over 10 years ago, my very first message on the Stardock WB newsgroups, complaining about the lack of a skinning tutorial, got me flamed by Brad himself, lol. At the time Brad claimed WB was still in beta (it wasn't even version 1.0 then) and that was the reason why documentation wasn't available.
Well, been a long time since that, and skinning documentation is *still* not officialy available, hehe
The real issue is that we developers are all tech oriented people, and writting documentation for us sucks, it's very hard to do properly, and takes time away from other things - not to mention that skinning documentation needs to be updated constantly.
AFAIK, you won't find detailed skinning documentation for any Windows customization applications, Stardock or otherwise. Even Winstep is now guilty of that same sin, in that Winstep used to have a very detailed User Guide and now, since the new UI, it has only a FAQ (in fact, and until the individual Winstep skinning app is ready, you can't even make new skins for Winstep unless you use the older v9.x version, which is what WebGizmos does).
Whatever the reasons, this is not conductive to introducing new blood into skinning. We (developers and companies) keep complaining that skinners are now few and far between, forgeting all the time that it is mostly our fault for not making clear and detailed tutorials in the first place. Winstep is now as guilty of this as Stardock, so, yes, I'm pointing the finger at myself too. 
Funny how that works. lol