Hmm. I just tried the Help! ones and they didn't seem to work very well for me. I had my wife push the pedal so I could watch, and I could see little bubbles going back down the tube into the brakes when she released the pedal. It wasn't like it wasn't working at all, but the one way functionality was not perfect. Maybe it doesn't need to be?
I ended up just using them like a regular bleeder screw and kept tightening and loosening. I mostly got them because my old bleeder screws were all gummed up.