I'd be using a hand mister to do it. Just not sure if they would take in the water and cause them to over water.That depends are you going to use a water hose or a mist sprayer. If you’re just going to mist them it shouldn’t be problem. Maybe even give them a day or so but don’t soak the hell out of them either.
I can't. It's a very fine white clay powder that got into my grow room from the central AC in my house. It can't be wiped away, only rinsed off.Use a leaf duster.