Actually, the simplest approach I think would be to write the blog using Live Writer. Publish it wherever you want in the meantime. Then you can open each post in Live Writer, and publish it directly to SharePoint when it's ready. Just a couple of click that way. This will also give you the chance to see what the post looks like before publishing.
I have to say, Live Writer is the bee knees when it comes to writing blogs in SharePoint! It's very easy to use, and handles images quite easily--it autogenerates thumbnails, and makes the image clickable in the blog (to show it full size). I've been telling all our internal bloggers about it, and they all love it (especially the non-techie bloggers).
Regards,
Mike Sharp