Need to keep at it, and some grease around the bleeder where the hose goes on helps, and even tefloning the threads of the bleeders has been recommended for mity vac so you're just not sucking air around the threads.
I've been having the same issue with a 71 pontiac i'm working on using a mity vac with new master, booster, all new lines hard and soft, new calipers and new wheel cylinders, and new prop valve. Everything i have is top notch quality, but the bleeding has been a real PITA. I really think the mity vac is just loosing it's charm, and i may get some of those bleeders with check valves where you just pump the crap out of the brakes with them loose until they spit only fluid...no opening and closing bleeders.
BleedersThis Post was from: https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?post_id=97544