I sowed them 12/19/20, so they're just over a month old now!
This is the grow light I use, in the mode where all three color lights are on, 12 hours a day. I had them on one of these until I took them out of the germination box (I bought it when it was about half the price, though, I wouldn't pay that). I had the box on the heating mat and I would spray the seeds with water to moisten once or twice a day. They germinated in 48 hours, super fast. They're the lithops mix from Mesa Garden.
I just used a plastic cup. I have seen many people on youtube successfully use a plastic cup. In the future, I'll use terra cotta. I've had a lot of them explode the last couple weeks. =[ It mostly seems to be the ones that rest against the moist substrate that explode. Next time, I won't sow them as densly. I also won't use as much play sand to sow them, it really soaks up water. I honestly wasn't expecting the level of very fast germination I got. When I noticed them starting to burst from moisture, I acclimated them to the air over a couple days using the vents in the germination box. Now I bottom water them once every other day to every day. Make sure the roots are fully covered with substrate but try to keep substrate off the sides of the lil babies. I've had quite a few shrivel up because part of their root was exposed and dried up and they die super fast.
As for the substrate, I used about 40% pumice, I use this, it's sifted very nicely. It's dusty, but the pieces are evenly and perfectly sized. That's not the pumice pictured in the cup, though, that was a cheapo Amazon "pumice" that I'm not buying again. I use about 20-25% of this med. grain sand I get from Lowe's. I like this sand because the grains are even and around 1mm so it gives some variation to the substrate but is much larger than a fine sand. I use 20-25% organic potting mix for the organic bits, not miracle grow or any brand that have hydration pearls. I pull the larger pieces of bark out of here and try to keep the substrate 4mm or less. I will use 10% organic material or less in the non nursery pots after I report them into terracotta in like a year or earlier if it gets too crowded in there, but I'll use the same pumice and sand.
To sow, I mixed about 100 seeds with about a tsp of play sand. You don't need nearly that much play sand. I sprinkled over the top of my substrate that was already moist. The sand wicked up enough moisture to dampen the seeds, then I sprayed them probably twice a day til they germinated.
It's been a learning experience for sure, but they grow so fast there's new stuff to see with them everyday and I am SO excited for them to start showing off more of the traits of their varieties.
I often use a seedling mat under the bowl/banneton while proofing in the winter as a convenient way to keep it warm without a full proofer. Something like this: https://www.amazon.com/VIVOSUN-Waterproof-Seedling-Hydroponic-Standard/dp/B00P7U259C
I've combined a seedling heating pad with an inkbird temperature controller. The thermometer is placed in the kombucha and will turn on the seedling mat when the kombucha temperature temperature drops below a +/- threshold. That way the temperature is more consistent over a 24 hour span. Had really good results and never had mold issues with the probe touching the kombucha.
https://www.amazon.com/dp/B01486LZ50/ref=cm_sw_r_cp_awdb_imm_t1_q2nOFbKW4KKPH?_encoding=UTF8&psc=1
https://www.amazon.com/dp/B00P7U259C/ref=cm_sw_r_cp_apa_i_T5nOFb7XV69R9?_encoding=UTF8&psc=1
The one I got from Amazon has been a lifesaver for starting absolutely anything — VIVOSUN Durable Waterproof Seedling Heat Mat Warm Hydroponic Heating Pad 10" x 20.75" MET Standard https://www.amazon.com/dp/B00P7U259C/ref=cm_sw_r_cp_api_glt_i_K7QHVJ0EN0MR4CETE9BX?_encoding=UTF8&psc=1