I watched a show recently on TLC which showed cleaning "concrete" with a pressure washer followed by murasic (sp?) acid washing. This "might" work for bricks as well. The show cautioned that the pressure washer should be respected because the spray could break glass or even break the concrete. You might try this, however I'm no masonery expert. Good luck!

Hammer and chisel. That is why masons hire laborers.

I agree with Dr. Home. The hammer and chisel is the best approach. Spring break is here, if you have any kids maybe they'd like to help.

Hammer & Chisel
AND Safety Glasses and Gloves

I've done this because we were looking for an old brick look...If you're not,I strongly recommend new brick!!