I use dummy rounds all the time in my High Power and GSM Clinics. Normally we have classroom training prior to shooting.
In demonstrating and practice loading dummy rounds come in handy. Simply don't let live rounds in the class room.
I make up dummy rounds by removing the decapper from the sizing die, leaving the spent primer in and stuff in a bullet without powder.
To mark them so one can instantly see they are dummy I drill holes in the brass. I tried painting them but often the paint jams up things.
They make dummy rounds for dry firing. If its for one guy and one gun they are great. If you have a class of 4-8 students practicing loading 'n such they are expensive.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071