surely somebody must know something??
It's not a true apprenticeship, but looking at Panturas site, it seems very apprentice like. (2 artists, no more than 5 extremely dedicated students, etc...). I think a lot of artists now a days teach in group settings like Ateliers and such and then perhaps form closer bonds with promising students they meet there.
Of course, this is all speculation based solely on what I've read here and there. I haven't had any experience with many art professionals.