I don't know what the seed looks like either, but I doubt there would be any problem sowing chaff and all. Not knowing the species, I'd say sow at 70F.

I don't want to discourage you but we've had little success with seeds. But, no loss tring if you have seed. I'd plant them directly in the garden (in grit, etc.) and be patient.

What we do is remove offsets (as small as pea size) and give them a bit of room to grow without being swamped by other plants. They have been incredibly hardy, even surviving our cold Canadian winters in raised tufa planters.

http://communities.canada.com/calgaryherald/blogs/gardenbuzz/default.aspx

Your best bet would be to read up on the sowing of cactus seed in pots with plastic on top (I get good results with 2oz takeout cups with clear lids). The seed is small and seedlings will be fragile until they've got a bit of size to them. Allow them to grow together until they're crowded, then divide them.

Orostachys are very easy to do from cuttings too, last fall my O. Iwarenge had 100 or so tiny offsets on long runners and they all went limp after the first cold snap. I snipped them all off and planted them in a couple pots indoors and they all rooted and took off. O. Spinosa is a bit more reluctant about offsets, but still produces about half a dozen before it flowers - and they're similarly good about rooting when removed, even when only the size of a lentil, when given good conditions (warm, out of direct sun and covered to retain humidity).