Do candidates ever write thank you emails to Congressmen/Congressmen's interview panels to follow up after an interview, or is that sort of overkill? What about after ALO/BGO/FFO interviews?
I did. In it I thanked the one in charge of my congressman's nomination process one more time (I met them in person at my interview) and politely inquired on when they would be getting back to their nominees.
Make sure you keep a professional register, and you should be fine.