Can't bleed air out of rear brakes

Standard hydraulic brakes do not need to be pumped to be bled. Gravity bleeding actually works best. You need to bench bleed the MC as outlined. One of the most important things that hardly anyone ever thinks to do is to bleed the system with master cylinder LEVEL. This is extremely important. Most times the MC is angled upward at the front and will trap air in the end of the cylinder. You need to jack the car up so the MC is level. Then starting from the RR gravity bleed until solid fluid comes out. Proceed to the LR, then RF, then finally LF.

Yep, I just crack the bleeder screws and remove the MC caps and let them drip for a bit. At first nothing might come out but give it some time and watch them bleed