Drum brake issues

[sqrlnts]

Recently my front left drum brake wheel cylinder started leaking. I have 4 wheel drum brakes on my 57 and the original rebuilt master cylinder. Luckily the brakes quit working near my house so no wrecks. Up to this point I had a very nice (for drum brakes) pedal.

I replaced the left cylinder and filled the very empty master cylinder back up.

Ever since this I have had a very poor brake pedal. Tonight I decided to bleed all 4 corners. I would pump the pedal several times and hold it in place with a board and started bleeding the LR wheel, then RR, then RF, then the LF. The pedal got somewhat better but would come and go when doing the fronts. At times the pedal would firm up and then I would lose it completely.

I have self adjusting rears but not front. I made sure the brakes were adjusted properly before bleeding.

I am wondering if I need to remove and bench bleed the master?
I have read that I can pinch the rubber lines to eliminate the wheel cylinders. Also wondering if I can get an inverted flare blank off to do the same to the rear since it has a braided AN line.... Any ideas??

Thanks in advance.