Lots of good advice here, but I will add mine anyway!
I use Polyscale Daylight Red (has a definite orange tint) mixed with Engine Black for the most part. Each time I paint a building I mix up a fresh batch and that way no 2 are exactly the same.
I've also used Boxcar Red (ok) and Tuscan Red (better) on buildings which I'm not planning to paint all at once. That way no worries with matching.
Tuscan Red is not all that opaque, so you can get varied brick colours by putting an extra coat on just some of the bricks. Painting bricks one at a time is not for everyone, and I sure don't do it on all my buildings. The really dirty ones don't need it.
For mortar instead of a mortar wash (which I've tried and failed miserably at) I use Spackle. Rub it into the grooves. Scrape off the excess.
Also, not all buildings are plain brick. Many have been painted over the years.
Below are some examples of the various techniques I've described.
#1. Dirty, no mortar lines.
#2. Red and black mix with spackle mortar.
#3. Tuscan Red with spackle mortar (and detail in top R corner)
#4. Painted version
#5. Another typical paint scheme
:thumb: Val