Pour a small amount of light gray paint onto a paper plate. Dip a sea sponge into water and wring out the excess. Dab the sponge into the paint and then directly onto the wall to create the color of the mortar, or masonry cement. Apply where you want mortar lines to appear. Allow the paint to dry for 4 hours.
Place ¾ -inch painter's tape onto the wall in horizontal lines over the gray paint. The width between the lines of tape is the width you want your faux bricks to be. Estimate the width unless you want precise bricks; then use a ruler and level.
Add vertical strips of painter's tape to the wall to finish blocking out the bricks. Rub all tape to the wall firmly with a plastic putty knife.
Using a drill and a mixer attachment, whip a bucket of lightweight joint compound until it has an even consistency. Add a small amount of distilled water to the compound if it is too dry. Use the putty knife to wipe thin layers of joint compound onto the brick sections, covering about 90 percent of the wall. Allow the joint compound to dry.
Pour three different shades of red or beige paint onto three different paper plates. Dab a damp sea sponge into each color and then directly onto the joint compound used to create the bricks. Continue to add paint until the faux bricks are the correct brick color and all bricks are painted.
Pull off the painter's tape slowly. Cut the tape with a razor blade if it is stuck. Paint any gaps in paint, using a small artisan brush. Allow to dry.
Pour clear flat-sheen polyurethane into a paint tray and use a paint roller to apply the polyurethane onto the entire faux brick area. Allow the polyurethane to dry for several hours.