I recently obtained a slug of Belgian (Chimay) brewer's yeast to use in baking. I have a sourdough culture I started from scratch some time ago, and read up on starting a culture from brewer's yeast in a similar manner. I did a pretty astute job of isolating the yeast from the trub in the slug I had, and sure enough, the starter took off about eight hours later. I made my first batch of preferment using this starter a day later. I let it ferment at room temperature for another 12 hrs, then put it in the fridge and made the dough the next day.