Soft Peddle

I assume you adjusted the shoes pretty tight. If not, you would have a lot of lost travel. I always bleed with vacuum and my wife slowly pressing the pedal. I usually see bubbles, but they are from outside air sucking past the bleed threads. You can see that even without vacuum from the venturi effect, i.e. the fluid falling down the drain tube sucks a vacuum at the top.

I don't know how a bad MC could entrain air, as long as you keep the reservoir full. Problems would be it either leaks or doesn't build pressure from seal leaks. New MC's can be bad. I had a fairly new rebuilt one fail. Took it apart and found a cut seal because the rebuilder machined the bore and left a sharp edge on the side ports.