To create a large batch of starter for many loaves (30), do I just keep feeding until I get the amount I need? How often? 8 hours or more between feedings?
It probably won't take much either. My starter is a 67% one, that I feed 1:3:2 (starter:flour:water). That grows it very fast. 2 oz becomes 12 after one feeding, and that 12 becomes 72 at the next feeding. I find that feeding works fine every 12 hours at room temp, or over a couple days in the fridge.
Assuming you are making 1 1/4 pound loaves that would be about 40 pounds. Assuming a 4 X expansion each time that would require 8 pounds of leaven which would (working back) require 1.6 pounds, then 4.5 ounces. So 1 ounce with three feedings should do it!