A trial run is definitely good. It will help you figure out how much feed you will need to ferment in a batch. If they eat it all and seem to need more, you can always give them some dry feed late in the day. Hopefully all your birds like it!
On a 3 day cycle you would have 3 batches going at once. So you have 3 days worth of feed going at a time.
Depending on the type of feed you start with, your container may need to hold up to 4 times the volume of the dry feed when wet. Some feeds swell up more than others when you add...