I have the Bravo and used the Youtube video noted above to program it. It works well, but I also had the same question about modulating the throttle axis during beta for taxi purposes.
I solved this by programming the TOGA button to HOLD REVERSE THRUST. Now, when I press the TOGA button (on the throttle) I can modulate beta to slow down during taxi.
I kept the original Youtube throttle settings for max beta. So, when I land and want to reverse thrust, I still pull throttle all the way back and engage the max beta position.