I almost hesitate to write this, since it is unconventional and requires some care. At least in the old Mooney, the master cylinder under the floor sits flat and the inlet/outlet also horizontal. As Mark indicated, the air can get stuck there and difficult to purge. I’ve tried bleeding right there, but difficult doing that solo, and still opportunity for air to be at the top of the cylinder. Getting some flow through there may help….but I’ve always ended up with just a little softness. Here is where it gets unconventional, but worked for me. If I recall, the forward fitting faces left. While flying, with plenty of speed and coordinated, perform a relatively steep, climbing, right hand banked turn……..and simultaneously pump the brakes. This allows the final few bubbles to to find their way to the left forward fitting and to the reservoir. This is not a surrogate for a full brake bleed….just those final few bubbles. Results may vary…use care…perform clearing turns and don’t spin…have fun.