Texture paint is a good choice for covering the rough surface of rustic or worn exterior bricks. Textured paints cover cracks and gaps well, allowing you to smooth and transform the surface of a brick wall. The results you get depend on your approach. If you want to keep some of the texture and feel of the bricks, use thin coats of paint and primer and only a single coat of paint. For a smoother, more finished look, use thicker and more numerous coats.
Put on rubber gloves and goggles. Mix 1/2 cup of trisodium phosphate (TSP) and 1/2 cup of washing powder into 1 gallon of water in a bucket. TSP is quite caustic, so you should always wear goggles when using it.
Spray the wall with a garden hose to knock off big clumps of dirt. Ideally, use a high-pressure nozzle to really give it a good pre-cleaning.
Apply the TSP detergent solution with a brush. Work it into the grout and along the brick. Trowel Trades recommends using a "long-handled, stiff fibre brush" for this purpose.
Spray the wall again to wash off the cleaning solution.
Paint the wall with a latex-based primer designed for exterior brick. Hometips.com recommends using a 1-inch nap roller.
Use a paintbrush to go back over the wall and work primer into any areas you missed. Allow the primer to dry for as long as specified on the container.
Paint the house with textured paint specifically designed for masonry. Apply it with a roller, and retouch it with a paintbrush, as with the primer.
Allow the paint to dry. Apply a second and third coat as you wish.