bleeding my master clutch cylinder

alr so ive replaced my master cylinder for my clutch because the fluid was back and grey. ive bled it prolly 50 times like a whole quart and theres still a crazy amount of air in the master ( frogot to bench bleed)
so ima buy a vaccume bleeder, ive seen people use it from the slave bleeder and directly fron the master inlet, which shiuld i do it from.
and whats the max vaccume i can pull in it. 10-15 inch of murcuery?