If you have something legitimately news-worthy then I've found a press release can be the "in" to getting attention from big blogs you don't have an existing//personal connection with. Check out businesswire and marketwire (especially Marketwire's "Tech Hotspots") to help get your release into the hands of people who want to write about exciting stuff.
Otherwise, I think the core of your question is more about marketing. My first recommendation is to have the link to your co in your news.yc profile + link to it in your story submission. Second, I'd suggest your best strategy should be to find the 2nd and 3rd tier blogs that the bigger blogs look to in order to find new companies not on their radar.
Big blogs are like corporate radio: they both want to be responsible for "breaking" a hot new [band//company], but both are unlikely to make that call without others in the "underground" having said it first.
An extension of this would be to find who the big bloggers follow on Twitter, and then figuring out ways to get those people talking about your product positively.
It's amazing how quickly rave reviews trickle upwards with little intervention.
Good luck! :]