How do I start theming the ribbon? I'd like to use blend for it. I've managed to load some of the default themes, and edit them in my local copy, but is this 'the way to go' ?

And are there any reference of putting my custom theme in a seperate assembly?

[edit]
Okay.. I asked this.. because I run into some trouble.. when I put the theme files (base, brush and RibbonGeneric) into a Blend project, everything goes well. When I put them into my VS2008 project (to actually USE them ;) things go wrong.. I get a lot of parse errors in RibbonGeneric. Some are weird binding syntax I could fix, but in some of the Triggers it's not able to find properties on some objects. Hence, I cannnot use the Theme. Which is pretty annoying ;)