Multi-Site: How can I move a blog post from one site to another?

Hello,

I have a web community which is harming itself in terms of Google search ranking.

It is a site for writers and as such, it has articles about the craft of writing, etc, but then it also has book reviews, short stories, poetry, you name it and ... I'm fed up - they don't listen.

Well anyway, I read somewhere that Google treats each sub-domain as a separate website, so I'm going to create something like: http://bookreviews.writersdock.com and http://shortstories.writersdock.com and, herein lies the question: how do I move relevant posts from one sub-site to another?

Thanks in advance.
Sonny.