Yes the unwanted coach also slows people down, and that coach is often the person that watches too many videos and has to get his feet placed just right, and has to take several practice swings. He is usually the person that beaks around 20 targets per round, and really doesn't understand the game himself. And of course there is usually one person that always seems to have problems with his gun or with his reloads that slows things down. As far as concentration goes, our skeet range is next to the biathlon club where winter and summer events are going on fairly often, and we are next to a big pond where there are often thousands of geese making a racket, so quiet is often mot a possibility. Then again, if you get a squad of experienced people that simply step onto the station, and call for the targets, and shoot, the round goes very quickly, even with a few comments as shooters move on and off of the station.
As to the absolute best way to slow down a round, have two or more beginners, that haven't watched a round of skeet, using guns that they aren't familiar with, with someone that wants to coach the finer points with each new shooter. That combination has resulted in over an hour for one round of skeet. If a beginner watches a round or two first, is made familiar with the gun before the round, and you just make sure that they are safe , and don't worry about a lot of coaching, the round is far more enjoyable for everyone.