Oh yeah, that hits home. Helping my uncle with his brick patio, we dry brushed and just made a dusty mess. His mason neighbor showed us the damp trick and it was like magic, totally changed the finish. I felt silly for not trying it sooner.
But that damp brush just pushes wet mortar into the joints... making it harder to clean out later. I've had to go back and chip away at dried gunk that a dry brush would've left loose. Sometimes the old dusty way is less work in the long run.