How much *&%^#$^ fluid to bleed rear brakes???

[Stocker]

[Rant] Pardon my frustration.... after replacing the MC (and bench bleeding it), front hoses, & rear shoes, I started bleeding the system, starting with rears first. Though I wonder why that should matter since the front & rear are two independent systems.....

Anyway the parts house had no clear tubing (to run from the bleeders to a catch can), so I used black hose. Pumped (with the brake pedal) fluid to each rear wheel cylinder, then each front caliper. Maybe this also pumped air into the lines? Maybe I should have been more patient and let gravity do its thing. Careful not to let the MC go dry. This took close to a quart of fluid.

Didn't like the black hose b/c I couldn't watch for air bubbles leaving the bleeders, but I found some clear tubing at a hardware store. Good!

My wife then helped me bleed each corner. Never could get the air out of the rear lines, gave up and bled the fronts. Didn't take long and they were good. Went back to the rears (actually left rear) and so far have gone through more than three 12-ounce cans of fluid. Still getting air bubbles. Fluid is coming out clean and I'm about to start pouring it back into the MC rather than buying any more new fluid.

What the heck am I doing wrong? Should I just keep at it and the bubbles will eventually be gone? Right now it seems like they are somehow being introduced into the system. I'm stumped, I'm frustrated, and this just makes no sense to me. We've spent at least a couple hours and are still purging air. [/Rant]