I walked straight to Z11 where the sign was out pointing to the bus connection to non-Schengen B gates. A bunch of people were sitting around but I decided to stand at the front of the queue (aka I made the queue). I waited about 5 minutes and then they opened the gates and let us down the stairs and around the maze. You can't get lost. Just follow all the arrows pointing you to the bus.

The interesting thing is the bus was 50%+ full when I got on. I have no idea where the earlier people boarded from. After a bunch of people from where I was waiting in Z boarded they stopped those in the downstairs/ground-level hallway and didn't let them board. So a bunch of people who were sitting around were out of luck and had to wait for the next bus. After we were boarded full the bus sat there for another 5 minutes before we started moving but I believe that was due to the road construction in front of the bus stop and the temporary traffic signal that was setup. Once moving we made it over to the B gates in just a few minutes and let out to walk upstairs to the non-Schengen part of B terminal without needing to re-clear security.

I'm very glad i read this thread before my ex-US flight departed to FRA or I would have not realized there's a shuttle bus connection.

Thanks,
-RM