Anyone know how to get a special duty assignment without going through branch?

I find the "power" given to Branch Managers to be one of the biggest issues with the Army's personnel management system. These programs---Drill Sergeant, for example, or the range of other special duty or broadening programs, are designed to benefit the whole Army, are DA-level processes, so why should the parochial, small-minded interests of one Branch give that Branch a veto over a higher level process. Let folks compete, and let the selection boards choose the best candidates.

Branch has to release you as far as I know, but if you volunteer it's after you apply and it drill sergeant is a powerful entity

Even if you don't start with branch it will always be approved by branch