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.