I have traded with Malej Jarda (Gerado) for a couple of years and got my Digitostigma etc from them, plus also met the two of them who grow the plants and collect the seed (Zlatco Janeba and Jaroaslav Snicer) at The Cactus Explorers Weekend in the UK a couple of years ago. One of them was also selling plants at the BCSS National show in 2012. They do collect seed of the latest novelties in habitat, raise the plants and produce seed for sale from them very quickly, since it is often the E. Europeans who find the plants in habitat first before they are even described and named. One of them is editor of one of the E. European cactus magazines I believe, and I think one used to live in Mexico for a while. You will also find their articles in various cactus journals, including the Cactus Explorer:-http://www.ibiologia.unam.mx/slccs/www/ ... 202009.pdf
I have some Strombocactus corregidorae seed from them when I get around to sowing them. As Snowcat says these dust like seeded plants are not easy to grow unlike many of the larger seeded cacti, since moss etc seems to grow in the seed pans quicker than they do, therefore you may be better off with the "baggie" method using sterilised or microwaved compost.
If you get 5 seeds of A. valdezii in a packet you will think they have sent you an empty packet as the seed is so tiny and dust like, therefore you have to be careful opening it up and emptying on top of your compost. Probably examine it with a magnifying glass to even see it before sowing!http://www.bcss.org.uk/foruma/viewtopic ... 1&t=153791