I'm in Japan with the Marine Corps. I signed up over here so it's all I know.
I had a special form from SU that I had to get command signature on. This was for Military Status, not Military Override. Basically, it has two blanks for the command to sign saying I am allowed to sell to those on base (it should say to SOFA status personel IMO), and that I am allowed to recruit on base (per SU's requirements). It was fairly easy for me on this base, but I know others have had a more difficult time depending on the country and commander. We have no quarterly minimums here.
Good luck!