Dr. DIFF cobra brake/ master cylinder question

Give it a try one time. Air escapes through the holes in the bottom of the master. If you look inside during the process, the air bubbles are visible as they escape into the master. The system is closed when plugged and once all the air vents through the holes the system locks. The re-builders include plugs for that purpose and recommend that procedure. Been doing it exclusively that way with excellent results. Never had air in all the MCs I’ve changed.