I would highly recommend not spending time as a single developer submitting proposals, and instead start trying to build relationships with some of the winners/participants of past IARPA tournaments. They regularly bid on these IARPA programs and have some level of success. Getting on one of their teams as a SME or with a specialized offering is a great first step. If you're in the area, the proposer's days can give you an opportunity to get up in front of everyone and talk for a couple minutes about you and your capabilities to get your name out there.