I dunno...overnight?

I've never done it myself, but had good luck with the "one man bleeder kits" you crack open the screw, attach a rubber hose to it, going to a small bottle with a magnet, and mount it up higher than the bleeder screw. go up and pump the brakes a few times, keeping the master full. As the air pumps out, it "floats" to the top, and into the bottle, eventually you'll have good solid fluid in the rubber hose, and you can go ahead and close the bleeder and move to the next wheel.

don't forget to start with the master cylinder first! crack open the lines and slowly and steadilly pump the pedal. I never believed that it needed to be done myself, I always figured "what difference does it make if the brake lines are loose at the master or not? pump the pedal, it should push the air out and into the lines, and ultimatly, out of the bleeder screw at the wheels" but after pumping and pumping and pumping, I never got a full pedal. cracked the lines at the master and got out a lot of air, and then the pedal was rock hard! go figure!