Generally, you have to think big and write small.
Articles are around 300 t0 500 words. But blog entries can be (and book chapters usually are) much, much longer than that. A small book contains at least 50,000 words - this is then around 100 articles.
I don't know about you, but I only get started about 500 words, generally running 1500 to 2000 words when I'm really wound up about something - I'm just outputting what has already fallen into place internally, the dam just bursts and it all comes out...
So for me to sit down and write a half dozen small paragraphs is like writing adcopy for a one-half page car or clothing ad which is mostly pictures. Painful in word selection and much slower than simply writing the thing out of whole cloth.
What to do? The solution is pretty simple: write it however you want, then break up your article with subheads every 300-500 words (or less). This makes it easier to read and also allows you to split that blog entry into smaller article-directory articles.
Now, your title will need be (Title) Part 1, (Title) Part 2, etc. A 1500 word blog entry would then generate between 3-5 articles. 2000 words might get you 6 or 7 articles.
Doesn't mean you write in longer paragraphs, just the opposite. Writing for the web is covered elsewhere, but short and simple (KISS) is the maxim to use.
The great thing about this system is that it enables you to simply have a title and subhead for each article - and that section flows. Next part has a new subhead and so on...
Your part is easier. Sit down and write your heart out. Post it on your blog with subheads or none.
Then copy/paste it into a nice text editor (like NoteTab Lite/Pro). Put in the logical breaks with subheads. Check to make sure that these sections total at least 250 words - you can have a couple subheads if you want. Save and save often as you go.
Now, with it all set up in plain text, you can copy/paste the articles into your article submission program and knock yourself out submitting them to all these. Don't forget to Google the title so you have a distinct main title (which has all these parts to it).
The Blook part comes in when you save that article to a folder where your book is being saved (and coming along nicely, I hear...). You just wrote another chapter or a big part of one. If you just wrote 2000 words there, then you only have another 14 such chapters and you're set to publish - well, almost.
If you want to be precise about it, then prepare an outline and blog based on your research. I don't write that way, myself. Sure, I've done a lot of research, but my bloggings are often inspiration as I find a solution to a problem that's been plaguing me. Or I'm just racking along checking things out and then an idea comes to me I need to record for my research records (and your amusement).
For that last inspired way of writing, simply write your outline and then assign/rename the text files according to that outline. And revise your outline when you find you've written more about something - or less. Now, you can always write more - and many sequels are due to the fact that the writer never really finishes researching something s/he loves to write. But what is coming out of that keyboard now doesn't have a great deal to do with the original thought sequence - or is much more advanced and belongs in a follow-up book.
And there you have it - how to blook your way to success, article marketing your book before you even publish it. Don't forget that when you have 5 or 6 articles, you can make a special report or ebook out of it. So you have something to give away from a single blog entry - which will give you email subscriptions, where you can sell them something to support yourself while you finish your next magnum opus.
Wishing us both a flood of success...