I never bench bleed master cylinders. I install them, leave the fittings slightly loose, and just bump the pedal at the top of it's travel about an inch and let it return several times, and tighten the fittings. The air is forced out around the fittings and bleeds very fast. By doing this slight movement at the top of the travel allows any possible trapped air to return via the ports into the reservoir.
When you have no helpers, you find ways around the conventional methods. Been doing it this way for over 50 years, so I've done dozens and dozens this way.
I also use gravity to bleed brake systems, which some people can't wrap their heads around. Physics never changes, air rises through a column of fluid, and fluid falls in a system, basic physics. I don't make things more complicated than they need to be. YMMV...............
