Let's assume that the paint in question is some latex paint that has gotten onto the bricks due to a less-than-perfect application. I've had limited luck with the following...
Spray on oven cleaner until paint softens. This is best done on dry bricks on a hot day. MAKE ABSOLUTELY SURE that you wear proper protection, including:
Once paint is soft, rinse the oven cleaner off. Avoid splashing, because the oven cleaner may contain LYE, a dangerous caustic. Next, blast it off with a pressure washer. Test a small area first, and make sure that you do not damage the bricks or mortar with the pressure washer.
This job is an absolute mess, and it wouldn't be a bad idea to wear a raincoat and hat, in addition to the above gloves and goggles.