My first step was to paint the entire wall, basically bc it was a flat paint before and I changed it to eggshell.
Obviously walls vary in size so you will just need to determine how close you want the stitching.
We tied a pencil at the end of a rope and then tacked it in the corner then drew from one side to the other to get the long line. Make sure u hold the pencil outright and not slanted at all! Then do the other line in the opposite corner.
I traced the line with a thin paintbrush using a gray paint we had already. It's ok if the line isn't exactly the same thickness ! If u look close you can see mine varies in thickness.
The best thing I did was make a stencil from a scrap piece of cardboard for the stitching. And I didn't try to draw the stencil exactly the same, I made some shorter and longer just to get a different stitch
Using this stencil made it so much easier than trying to do it free hand! I did one line with the stitching one way and the other line with the stitching the opposite way and did them about 2 inches apart.
When I was done painting all the stitches I added a little black with some red to make the shadow at the end of each stitch. That really did add a lot to the overall look. You can see in the pictures with and without.