To bleed a master cylinder, rig two connections at the outlets of the master cylinder to two tubes that go back up and over down into the reservoirs. Make sure they are full. Have an assistant slowly push down the brake pedal several times until there are no air bubbles. Having said that, I have only bled master cylinders when I was replacing them. The normal routine of bleeding the brake lines is probably sufficient, unless you have some reason to believe that there is a problem with the master cylinder.