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Bleeder on the slave would be pointless in any event, as it sits BELOW the master, and pushing air DOWN a line just doesn't work well.
Injection bleeding works that way. I never do it but I've seen it done. Similar to what the video shows.
Pushing the actuator rod in usually will force the air to rise in the line. It's possible the seals inside are weak. That's why pumping the pedal works, but not quite all the way. Like a brake master cylinder going out.