I did some seeding out about 3 years ago. Those seeds came from my own plants, obtained in late Winter and sown out in April.
I simply prepared a fairly flat dish (with drainage holes) with commercial Cactus soil mix and spread out the seeds as they were. I added a fine cover over the whole thing by rubbing some of the soil between my hands over the flat. I sprayed some water on it and also kept it just a bit damp for the next few weeks. I don't remember how long it to germinate, but it was fairly quick, I think about a week, but I don't want to swear to this
and I remember a ca. 95 % germination rate. I should mention that I did this in my very sunny greenhouse with good ventilation, so I wasn't worried about mold. As soon as temperatures outside were warm enough, I moved the cute seedlings on to the deck.
Nothing fancy....