To remove paint from brick, start by spraying the brick with a hose. Mix a solution of 2 pounds of trisodium phosphate (TSP) or a strong detergent, apply it to the surface, and allow it to soak in. Then scrub with a stiff nylon-bristle brush (don’t use a wire brush). For resistant spots, repeat several times.

If scrubbing with this solution doesn’t work, try using a water-based paint stripper (first test it where it won’t show).