Thanks, very informative.
I am assuming 'Tallus' to be some kind of very fine sand. Is that correct?
Yeah, as Richard says it's the railway grit you usually see hanging next to the Jarvis stuff in model shops.
In the case of the Byzantines and Beja (is the mini's I've been mucking around with of late) I've mixed it with sand and some other kind of slightly larger pumice-ey small rocks (probably from a railway/model shop too).
I haven't left any of the filler showing through either.
Apart from those minor details the method is the same.