I've got a few of these going right now; they seem to be doing well and are starting to take off now (about 4 weeks after first signs germination). I made a soil mix that was probably overkill on the number of ingredients but had fun making it anyway
I put in (approx. by vol):
Commercial cactus mix (4 parts)
Sand (3 parts)
Perlite (2 parts)
Some azomite (0.5 parts)
and diatomaceous earth (0.5 parts)
Since I had read that these can be difficult to start I decided to put a handful of seeds in 4 different containers (a 2.5 in. square plastic pot, one long cardboard tube from a paper towel roll, and 2 more shorter tubes)and put two of each above my fridge and by a window. One on the fridge was the first to pop up but by then the window temp was probably up around the same so it didn't seem to matter.
The germination rate was fairly low (I sowed 24 seeds and got 5 to pop but lost one whilst trying to move it).
Attached are the seedlings as they are today
I've got a few seeds left and since I read that their viability drops pretty quickly with age, I'll happily send a handful to anyone interested and willing to get them into some soil pretty quickly