The dual circuit brake MC has a floating piston in it. If one circuit fails (no pressure fornt or rear) the piston slides off center - pressing the switch for brake warning. If you bleed just one wheel at a time, that's what will happen.
The f and r are really independent circuits, so just bleed both on one side. Try the brake caliper check valves available at centerline or IAP if you don't have three people to do the job (one at front caliper valve, one at rear, one pressing the pedal).