The only problem I have with the pushback command is I can only go strait back. The 1 or 2 key command for left or right does not work. More times than not, I can pull back myself with thrust reversers or beta if I am flting a propjet.
The left brake is "F11" and the right brake is "F12". See if that helps at all.
You need to press 1 or 2 immediately after the Shift-P. It will still push straight back for a ways, then turn. Be patient.