There is a solution to that bubble in the brake line where it runs uphill from the master cylinder.  I have a pressure pot, but that bubble just won’t go downhill.  Solution is remove the cylinder from the pedal and position it uphill from the bubble.   Or, put a “T” in the line at the high point, and a radiator drain valve with 1/8 npt thread.  Then slowly crack the valve and push the bubble uphill through the valve.  An icemaker water valve will also suffice