This would depend on the amount of work you want to do yourself. The easiest way would be a pressure washer. Just wash the brick according to the washer's instructions. Pressure washers have come down greatly in price or they can be rented at your local rental store. A consideration when removing bird droppings or leaving them alone is Histoplasmosis which will greatly affect your health. A Clorox solution spayed on the droppings before removal will greatly decrease your chances of getting the disease. If you have a small amount you might consider spraying them with a Clorox solution. Let it sit for several minutes to let it act and then scrub with a detergent followed by a good rinse of plain water. Below is a link to a commercial product made for this purpose.
This would depend on the amount of work you want to do yourself. Spraying them with a Clorox solution. Let it sit for several minutes allow the Clorox to kill the germs and to loosen the bird droppings then use scrub brush to scrub followed by a good rinse of plain water. Most of the time after the Clorox has set for a while the droppings can be removed using a common garden hose full blast.Experts will also suggest a mask and gloves, but if you are careful not to breath or get any of the bird droppings on you this precaution can be ignored.Below is a link that gives much good of information and confirms my information.http://www.cuhk.edu.hk/health_promote_protect/handle_bird_drop_general.htmHere is another with almost the same information.http://valletta.usembassy.gov/avian_influenza2.htmlBelow is another, http://chppm-www.apgea.army.mil/ento/TG142.HTM