I used 7/16 spacers but the brick is not all the same size I used small shims as well. I did a lot of research and this was the easiest way I thought to get the white I wanted and not risk getting different shades of white.

I appreciate the detail. The job you did is amazing. So to sum it up...

1. Did you use Ultraflex RS or Rapid Setting Tile Mortar as the substrate?
2. Then you used the Keracolor S for your grout?
   3 was the substrate mortar color also white?
   Thanks again for answering all my questions. I’m trying to get the same look!

I used a gray mortar. I would have to go back and find out what type, I purchased it from a local tile store. It wasn't rapid mortar. I went back and used a grout bag with the white grout.