Hi,
I am somewhat new here too, (coming up on my 6 month mark here).
I'll share this w/you and peops on AZ. I wouldn't even call this a "drill" as there is practically no skill in it, but if you try it I can practically guarantee that you will start your warm-ups with it.
I did this as the beginning of my warm-up at the pool hall before matches, and my team-mates practically laughed me outta the place!
its simple: scatter the 15 balls all over the table,(no cue-ball). Then , just shoot the balls straight into a long pocket. simple !
1st time : Do it long-table center pocket.
2nd time : Use English and cheat the pockets.
I have found this does 3 beneficial things for me so I don't care how silly it looks to others.
1- It gives me a sense of "Zen" as I am usually amped from caffeine on the drive to poolhaul.
2- It helps me get sightlines to be ready for the match.
3- It helps me get the feel for the table concerning felt & rails.(speed)<--- save the stripes for that.
Its something different rather than scattering the balls and taking the 1st shot I see for confidence, and going from there.