This bag- or box-method on sterile soil mix is the best way to grow Aztekium, Strombocactus, Blossfeldia and other species with tiny seeds.
The first year growth is typically very slow. You shoulnd't expect seedlings of more than 1mm in ø. I think and am pretty sure that prolonged artificial light doesn't speed up growth.

Jordi

1st of all, they do grow slowly, and therefore you should NEVER use any peat whatsoever in the potting mix, it will prove detrimental to your surviving seedlings after 18-24 months unless you carefully transplant, which is a risk unto itself.

Perlite mixed with regular garden soil (you can sterilize it if you wish) and some added gyspum is a good place to start. They must not be allowed to completely dry out for the 1st 2 years or so, this is best accomplished by keeping humidity high and the soil mix barely moistened.

Any container that can be sealed and opened for a few seconds every now and then to get some fresh air will do the trick.

Unless they are grafted, expect growth to be painfully slow, you may not notice areoles until the 2nd year. I think you may have your facts mixed up, the "boxed up" method will not result in any appreciable gain in growth rate. Max growth will be attained in a long (9-10 months), warm (80-85F daytime) and bright (not too much direct, hot sun) growing period with occasional dilute fertilizer with micronutrients.

Good luck.

These below are 10 years old, from seed.

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Five out of ten is OK.

Best growth is probably achieved with constant warmth (75F-85F) and steady light in a light box. Excessive heat will kill them, direct sunlight on an enclosed container will probably kill them, cooler conditions will slow growth down. People with warm houses will probably be able to grow them in a suitable bright window, but not in the sun. My house is too cold much of the time, too dark in winter, but it is very easy to stick them in a box with a light and forget about them for a year.