1995 Pontiac Grand Am Bleading My Brakes. I Can't Get Fluid

I can't get fluid to bleed out of the rear bleeder valve. I replaced the rear drums, pads, springs, cylinders, and the two little brake lines that run to the cylinders. Around two days prior I had replaced the front rotors, calipers, and pads. I had no issues bleeding the front brakes, but now that I have replaced the rear as described above, I can't get fluid to bleed out of the rear bleeder valves. I have ABS brakes and don't know if I might need some special tool to help the bleeding process.