Next, I wanted to deepen the grooves I had just scored so I took an emory board and sanded each line.
Here's a close up on how it looked after sanding with the emory board. My nails got a good sanding too :)
The next step was to cut in the vertical spaces between each individual brick. I had to experiment a bit at this point because I wanted it rustic. I tried a craft knife but I eventually found a bamboo stick that was just the right height to "punch" in those notches between the bricks. I was working with the grain so they often came out a little irregular. Good thing that was what I was going for!
I then base painted each block with shades of grey and a little white to become the color for the mortar. I was careful to get in all the cracks. At this stage I found that the paint softened the wood a bit. I took my handy bamboo stick from earlier and punched some of the holes deeper while the wood was still soft. After the grey paint dried, I brushed on red and terra cotta paint over all of the raised areas. This let the mottled grey paint show through as the mortar in all the scored areas.