There are many ways to do it. I use plastic transparent boxes with covers (15x20x5 cm??) - the one you use for food etc. I fill in 1/2 of the softest perlite. I water it slightly (to keep perlite in the box).
I sow seeds and cover the perlite and seeds with 1-2 mm layer of small pebbles (the smallest one you use for aquariums) to prevent perlite be taken away when you water the tray. I water the plants softly again to have everything wet and spray them against fungus. Than I close the box and keep it closed for several weeks up to 1 month.
Place the seeds not in direct sun. They should start germinating after 2-3 weeks.
After few months , when I open it, I have to keep them slightly wet all the time. Still keep more in shade. First repotting I do after one year.
Most of the plants from genus Haworthia (+ Haworthiopsis and Tulista), Astroloba and Gasteria are not difficult, you can grow them as other succulent plants. In Winter they excuse temperatures as low as 5 degrees. In Summer they welcome good ventilation. In nature you find them often growing under bushes, in grass or among rocks. This ensures them protection from direct sun and domestic animals (sheep and goats) which consume them without hesitation. Just a few species, e.g. H. leightonii, H. glauca, H. coarctata or H. reinwardtii grow in direct sunlight. From March till September I install 30% density shade cloth over my greenhouse and during the hottest months I add another 30% one. I have installed two larger ventilators inside greenhouse and they are running nearly 24 hrs a day. Basic rule - in South Africe the wind is always blowing!
