A blog post is not (or at least, it shouldn't be) a writing assignment you must prep for and deliver as a finished package. Let go of the idea that you must have everything nailed down, organized, and edited before you publish.
Blog your initial brainstorming. Blog your research. Blog your interactions.
The clincher to all this is to use your blog as your backup brain -- or at least as a public notebook. Get more mileage out of work you would have done anyway by changing your habits toward managing information and communication publicly. Instead of keeping your thoughts, notes, and conversations to yourself, post them.
That's a natural question, but the wrong one. The right question is, "How can I spend more time with my blog?" What can I do that I should stop doing? Rather than assume that blogging is an add-on, with the insinuation is that it is taking away time from "serious" journalism, how about treating it as journalism itself?
Fact is, if your blog is all that it can be, you'll be spending more time on it because you'll be part of a conversation with your readers. Talking with people -- blogging -- takes more time than solitary writing. But it has tremendous value. Why, as Amy points out, your audience may help you with your journalism.
Amy also has some interesting thoughts on journalism, conversation and community here, which I hope to get back to as soon as my deadlines will allow