Back in the stone age when I actually worked in a pool room, I would throw 4 trays out on the table for all the benefits Appleton cites. He has the balls layed out in formation. I would just disrtibute them evenly without balls on the rail. You can do any number of drills like this but the one takeaway is consecutive perfect strokes. Every aspect of fundamental pocketing and position will be addressed and uncertainties that plague the learning process will de-materialize. Even if you mostly get stumped, the idea is precision on a complete scale. This drill is the motherlode.