[KJUmp]

Originally Posted by AtlUmpSteve

No problem with what you say. BUT, if you allow the coach to do it, you can be sure a player will at some time, and you would be required to enforce that penalty.

NCASA stated my position. First time I see it, I change out the ball, and tell the coach he cannot do that (apply a foreign substance) to the ball. Rub it up, fine; the spit or dirt, only an umpire may do.

If he repeats, it isn't a G-d rule; he may not do what you specifically directed him not to do. And, before you ask, yes, you may direct anything you deem to be in the spirit (and intent) of the rules.

Bingo! Best answer yet.
Covers everything in the OP, shows good game management, works around the issue that ASA 6.6.A. makes no mention of other team personnel.