I just applied Foundation Armor WB to a flagstone walkway and patio. Application was a breeze with a standard 2 gallon pump sprayer. The square footage of coverage was as good or better than advertised. 5 gallons easily covered 950 square feet, with some left over for a partial second coat in higher-wear areas. It did not alter the color of the flagstone or dark-colored mortar. A subsequent rain did bead up on some of the smoother flagstones, but not on the mortar joints or rougher stones (did not expect it to.) Definitely recommend.