Combine 1/4 cup trisodium phosphate with 1 gallon warm water in a bucket. Put on a pair of rubber gloves and submerge a scrub brush in the liquid. Scrub down the brick wall, allowing it to air dry.
Squeeze out gray and white acrylic paint onto a paper plate. Dip a sponge into these paint colors. Press the sponge onto portions of the brick wall, covering the bricks with cream or gray paint here and there. When finished, a combined total of one third of the brick wall should have paint on it. Allow the paint to dry overnight.
Attach a piece of 80-grit sandpaper to an electric sander. Run the sander across the surface area of the wall, rubbing off the parts of brick and paint. Continue in this manner until you've created a rough, distressed look.
Run a vacuum cleaner around the wall, sucking up all the dust from sanding.
Take a hammer and knock off edges and corners of the brick here and there. Work slowly and methodically. You decide how distressed you want the wall to look.