I just went thru this drama too...
FSM has special tool that goes on prop valve stem that opens flow to rears.
Or it says open a front bleeder to simulate a front brake failure.
Make sure you bench bleed MC.
I did several times.
I bled fronts completely since I knew they would gravity bleed once I got some flow to the rears.
I don't think it helped that I had "speed bleeders" on all 4 brakes.
I might give the speed bleeders another shot now that I know I've got fluid to all wheels.
I learned all this the hard way so I hope not to make the same mistakes again.