Wash the bricks with TSP (trisodium phosphate) cleaner to remove dirt, grime and grease. Allow the bricks to dry thoroughly before proceeding.
Apply painter’s tape along the wall around the edges of the fireplace.
Paint the entire brick surface, including the mortar with a primer tinted the muddy gray paint color to match the mortar. Take time to completely cover the mortar.
Paint the mortar lines of the bricks again with a coat of muddy gray paint. Use a large, thick- bristled paintbrush to get into all of the nooks and crannies of the mortar.
Dab a light brick-red color over the bricks with a rag, one brick at a time. Rub the paint into the bricks with the rag. Thin the paint with water, if necessary, to cover the bricks well. Clean spatters from the mortar with a damp cloth. You can go back and touch-up the mortar when you are finished.
Apply the darker brick paint color randomly to the bricks to give a more natural brick appearance. Apply the paint with a sea sponge, dabbing the paint on individual bricks. This layer of paint will not cover the bricks completely, but should be done randomly to create a shaded effect. Work on small sections of bricks at a time.
Touch up areas of mortar, if necessary, when you are finished painting the bricks.