Think about it from their point of view. So to start with,
1, free bloggers need content. If you want to get your item blogged about you need to create the content yourself and make it easy for the bloggers to blog about your product - nothing less than spoon feeding them and giving them all the credit. Make it easy for them and if you are lucky someone will blog about it. But the reach of that blogger is probably limited and little or no return will come.
I hope this helped!