back brakes wont bleed

I always put a vacuum pump on the bleeds and have my wife pump the pedal as I open the screw. If it still doesn't feel like anything is flowing, try taking the bleed out entirely. Maybe crud is clogging up the bleeds. I would try it first without opening the front bleeds. That sounds strange. Seems like something should flow to the rear, otherwise how would your rears ever work? Hate to argue with a service manual, but sometimes they are too finicky like saying you need this special tool, or must measure the exact torque to turn something as you tighten the nut.