The bloggers have told me they get 50 requests a day for promotional stuff, guest blog posts and the like. And they ignore them all. Keep in mind, they actually want content. Unfortunately, they are not willing to do the work required to figure out if you're the one person in 1000 who's got quality content (I mean really, look at the quality of most guest blog posts. They're garbage).
Forgetting my specific technique (it doesn't matter), the answer is that you need to network with them. You need to determine what you have, in your niche, that will let you call these folks with something they'll actually be interested in - something THEY want, not something YOU want. Give them that, they'll talk.
Most people are unwilling to do what it takes in order to give the bloggers something the bloggers want. I provided a service for a year first, before getting to 3rd base with these folks.