Embroidering through multiple layers of coutil is more like repeated stabbing than stitching. It doesn't look too bad from about 4 or 5 feet away. Not perfect, but not terrible either. But it's moving along.
The tailor's shuriken has been vital in keeping the triangles a consistent width.
I ran the thread through beeswax and I haven't had a tangle up yet. Look at the difference between the two threads on the right, just separated from 6 strand embroidery floss, and the two on the left, which have pulled through beeswax.
I was concerned the wax would make the thread all gunky and it would dirty the fabric, but nope, it just smoothes it. Neat.