I don't tell the players no foul/keep your hands down i'm not doing their job for them either, the only exception is if on a corner being taken and there is a bit of jostling going on in the box i will say " Keep your hands to yourself "....... has served me well for the past 11 years
You are probably the exception to the norm then these days I would say. Certainly at level 4 and above proactive communication with players is a requirement, and I'd be worried if I assessed even a level 7 who wasn't doing this.