Has anyone used a pressure bleeder to bleed the brakes? I built one similar to this:

http://faculty.ccp.edu/faculty/dreed/campingart/jettatech/bleeder/index.htm

Today I gave it a try and after pumping a large amount of brake fluid on the garage floor due to a poor seal on the master cylinder cap I managed to get it pressurized. The only problem was at ~15 psi all I got out the rear passenger brake was a slow drip. I went up to about 20 psi but stopped there not wanting to damage anything.

I switched to a hand pump vacuum bleeder and could not get anything out. The old fashion stepping on the brakes worked fine.

Any ideas why the pressure didn't work? Videos online show a steady flow at the brake as opposed to the small drip.