There is a way to dump the air bags without auto-leveling. I did it already to check some jack blocks I made. You have to hit a button twice quickly, I just can't remember right now which button it is. I'll look at it again this afternoon.
I would like to say also that if I were you I would try to find a different option for getting your coach in your garage. I would be afraid that after starting the engine and backing up your bags will begin to fill again or they won't but you will not have brakes.
Good luck with everything.
2013 Berkshire 390 BH
2013 Berkshire 390BH