If you walk to the right place and stand there ...
(google maps)
https://maps.app.goo.gl/HP55HSXbRubX6qpe6
...all you have to do is hold your thumb up.
Most people driving out the back gate are already going to Graf anyways.
Stand in front of the last concrete barrier.
It's safe there for drivers to stop on the right side and pick you up.
If it’s rainy, the guard house across the street has a covered front porch.
If you think having a permanent Ride Share location at the back gate is a good idea, say so in a positive ICE comment to DPW.
While you’re at it, tell them if it'd be helpful to have two separate signs to stand beside - one saying Graf PX and another Graf Bldg 244, or if you think it’d be nice to have a bike rack nearby, or similar Ride Share stops on Tower Barracks near the back gate, building 244, etc.
Rose Barracks already has a permanent Ride Share stop for the front gate about 100m from the Commissary. Need a ride to the Vilseck Bahnhof? To Amberg?
You yourself can change the signs. If you pull the ends, they spin.
Just display your destination - and your thumb.