The group demonstration, is quite usefull when you have a lot of player who are considered weak because the first guesses aren't very good and when you have around 15 guys+ which you could scout for 10 points it is quite cheap in my eyes.
I'm not sure if I understand you correctly, but the breakdown of grey balls is always the same, 9 5 ball, 10 4 ball, 10 3 ball, 10 2 ball, and 9 1 ball. So you always scout 19 players with the group demonstration