I got these seeds from the CSSA. I was very happy to discover them on their seed list as pseudolithos seeds appear to be otherwise quite expensive. They were sown directly on top of my normal pumice/cactus mix. I since learned from the original research article on the genus https://www.jstor.org/stable/pdf/42792004.pdf?seq=1 that they do best sown with the pointy end pushed into the soil.
This photo was taken on Day 6 after germination. Four days after the seedlings came up, I added the white topdressing. Great germination rate, plus an extra bonus plant. I should probably get rid of it before it becomes a problem.
6/9 Update: all the plants are alive still. Wrinkles coming in. Definitely bigger than when they started.