There are many writers on BHW who produce brilliant articles. I would recommend trying a few out, and getting an idea of the quality of the work to begin with. Once you have found ghost writers who are able to construct content in the way you require, then you can "scale up", finding content which you would like on your blog, and getting these contacts to produce it. It is key to ask the right questions too (e.g. will it pass copyscape).
I tend to get articles written, and then try to rewrite the content in my own style - this is good because its usually difficult to get started writing a blog post, but if the ghost writer has already done the research for you, rewriting it should be a piece of cake.