Clutch bleeding help

I replaced the clutch and slave cylinder in my brother in laws truck but I am having problems getting the clutch line to bleed. I have no leaks so I don't know how I would be getting air in if that is the problem. I can not build pressure unless the pedal gets pumped a million times a minute then the master cylinder resevoir overflows. Can the master cylinder be bad? I even tryed to let it gravity bleed with no luck. The original problem was the slave cylinder failed. The fluid looked black/grey metallic. Could it have damaged seals in the master? Am I bleeding it wrong? Typical pump 5 times, hold, crack bleeder, close, repeat. The line has new o ring at each end too. Any suggetions would be great.

Well, problem fixed. It was a bad master cylinder.