Paint a base coat of the color of your mortar color, and then using a stamp made from
cellulose sponge, stamp out the brick forms. Start with dark red paint and do a bunch in a
random pattern. Add more paint to your pot, making the paint a bit lighter, stamp out
more, refresh your paint pot again, a little lighter and stamp out more. About four
variations in shade work out nicely, and you don't have to worry about color matching if
you need to go back and do touchup. The cellulose sponges give you a nice texture,
especially if your paint is nice and gloppy. Sponges are also cheap and work well with
water based paints.
Use a painting frame and a rigid horizontal bar to get your bricks parallel, and space them
evenly. Lay out a spacing line along your flat so that all your bricks on the different flats
will line up with each other. Also, distressing. How old is the wall supposed to be?
Mortar crumbles and cracks, bricks crack and get loose. Kids graffiti the thing and it gets
cleaned off, leaving a lighter pattern. Things hit it, damaging it and then repairs. Water
leaves residues from sprinklers and rain. Iron nails and screws weep rust stains, etc.
Depending on how close up your audience needs to be, we very much like using
Jaxsan 600 trowel grade applied to the surface and then stippled or sponged to get the
right amount of texture. This does not ad much weight to the unit like joint compound or
other methods. The mortar joints are lined out first using 1/2" spike tape that can pulled
up after the Jaxsan is applied but before it sets. The paint job is probably more complex
than the actual texturing process. Usually several coats of detail.