btw: This video of Danny Harriman breaking with closed bridge but similar technique to me is well worth a look:
http://www.youtube.com/watch?v=FHNL0fDLXy4
Notice how he lifts his bridge hand on impact. If he didn't, he'd probably damage his cue.
re: Efren coming up empty: Well everyone does sometimes. In 8-ball getting a ball better than 60% of the time requires a pretty good break. 75% is probably the figure for the power breakers. But some tables can be friendlier than others.
Of course, the harder you hit them, the more often you tend to scratch.
9-ball breaking is a different beast. I'd spend much more time studying racks than trying to get a really powerful break for that game. Still, if you can power break at 30+ mph, then you can probably break at 25mph with good control.
Colin