I haven't installed the beta yet, but I'm guessing that it's just like skinning the forum. If its anything else it'd just be idiotic on their part.
Might check on vBCodex - Community, Code and Coffee Wayne has been good about posting vb4.0 tutorials
shouldn't it take whatever skin your running already? Or are u trying to make a seperate skin just for the cms?
Im editing styles using vB4: Skinning Your Forum in 10 Easy Steps - Blogs - vBulletin Community Forum and it doesnt inherit from the stylevars..