Are Your Scale Buildings Mortar Bored?
To really look realistic your brick buildings need mortar.
Most manufacturers turn out a pretty accurate scale bricks in their sheets, but that is where the detail ends. Take a look at a real brick wall and you'll find there isn't much duplication. Some are scratched, some are chipped, many have a cross-hatch of gouges or scratches. Simulate these by dry brushing with a black wash (India Ink or black leather polish).
But the final touch mortaring, will have the most profound effect.I learned this from a Ken Sproranza clinic on weathering.
You'll need a bottle of sand-colored water-base paint as well as a dark gray; Both are mixed with denatured alcohol and often for use on the same wall section.
For a cheap, one session applicator, stop by your favorite electronics store and ask them to save you some packing foam (fine, 1-2-inch gray sheets). My favorites are the reverse egg carton looking used to pack sensitive electronic parts.
As needed, I cut off one of the nodules to provide a hand-held sop. Dip it into the paint mixture and rub across the brick surface. The next step is to wipe it from the brick faces, I prefer to use my finger for more finite control.
Fingers work good for this purpose as they don't dip into the mortar lines and swab out mortar and cleanup is real easy.