My 2 cents --- Aside from air being trapped in the ABS system which requires the pump to be activated, there are often high spots in the system (eg. front brake hoses) that require a good flow to get get the air flushed out (8 PSI is not going to do it) and having a second person on the pedal is the best way to get that. Air trapped in and just below the master can require some patience to let air bubble up through the compensating port. Vacuum bleeders will draw air from around the bleed screw so there is no way to tell if/when fluid is clear. They are nice for brake flushing though.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)