I'm wondering how one "gets his foot in the door" without actually visiting that particular unit? Sounds like you're just sending them an email, or talking on the phone. Not enough. Put yourself in the place of the unit looking to hire someone. Would you spend much time on a guy, based only on a phone conversation or an email with a resume attachment? Probably not. You need to visit the unit, preferably on a drill weekend. That way, you can at least show them that what you look and act like. Hopefully, you get the picture. Best of luck in your quest.
JJ