First, here is a handy tool I use for guiding my hand to make straight edges. I originally came across this gadget when I did electrical design in a previous life. I think I used it once back then.
However, I use it all the time now. Here is my first attempt at painting in the bricks. My thinking was to paint each line of brick then go back and lay in the cement in between each brick....WRONG approach. The brick looks pasted on. I wiped it down, though not completely off and tried another approach.
With just the suggestion of the line of brick showing, this time I tried going at it by painting the mortar lines in between the bricks. I almost felt like I was a miniature mason laying in one tiny row of brick at a time. I made sure not to draw a continuous line, rather I let the brush drag across and dot the background to pick out the texture.
My intent with this photo was to show you that I do not use just one color for the brick or mortar. Rather I let the brush pick up warm and cool grays and oranges and browns each time so that every brush stroke was varied.
I finally settled for not painting every brick. Rather I only did enough to indicate the texture and give the feeling of brick and mortar. I think by not providing every detail this allows the brain of the viewer to do a lot of the creative work to formulate what they see . I Think it also allows the viewer to see the painting differently each time it is looked at.
First review the goals of what you wanted in the painting. (I don't always remember my goals. That's what gets me into trouble.) I remember wanting to show the light and atmosphere, texture of the brick, and have a narrative.
Second, I look for places in the painting that attract the eye in an unintentional negative way...smudges, hard edges, places that need to be cleaned up or brought into focus, color temperature.
A few examples in this detail are the rooftop of the building above the truck. It has a bump that attracts attention, the bottom of the sign post disappears, some building details in the alley are too vague and need to be cleaned up. And of course I haven't started finishing the windows yet.