You don’t need a PR agency (especially one that does not get the social web). You need a blog.
Very interesting and valuable posting by Maddie Grant on how to write Social Media Press Releases replacing the traditional press release. It is important to realize that you do reach different audiences in the age of the Social Web: traditional media, online media bloggers/digital influencers, and the general public.
There is one point I do disagree. It sounds to easy: Open a blog and you are done. You do still need your agency or at least a capable writer to collect and write your Social Media Press Release. It is even more work to write it up, because you do collect much more information, in particular background (links, pictures etc.).