Dig a small channel a few inches deep along the base of the wall. This will allow the render coat to begin below grade, eliminating the possibility for an unsightly transition line.
Clean the brick and mortar thoroughly. Use a pressure washer, strong spray from a hose or a suitable cleaner to remove all dirt and mold from the wall.
Cover all windows, trim and other vulnerable surfaces with plastic sheets, tarps, tape or any other suitable protective materials. Remove any fixtures that can be detached.
Prepare the render. Mix the powder into water or stir render purchased as a liquid until the desired color and texture is reached. Render should be prepared immediately before it will be applied. In most situations it will be ideal to apply multiple coats of render, as each layer of render should generally be no greater than 3/16-inch thick, unless otherwise specified by the render manufacturer.
Apply the first coat of render. If the mortar joints are deep, the bulk of this first coat will be used to fill the joints in. Use a trowel and rubber grout float to fill in the joints and run a moistened paint roller or wooden float over the work area to achieve a smooth finish. Work on only a few feet at a time and, if the edges of the render start to dry, spray the material with a fine mist to maintain a damp and workable edge. Let this and each subsequent coat cure for at least a day before continuing with the next coat.
Apply the second and any additional coats of render. Prepare these render coats by mixing in any desired pigments. Place render in small sections at a time with a grout float or holding hawk and trowel. Use a wooden float, paint roller, sponge or straight edge to smooth the render surface, check for evenness and make corrections as needed.
Finish the surface as desired. In some cases, the final coat of render is used as the top coat while other situations may call for the application of primer and paint or waterproof sealant.