I imagine it'd be straightforward enough- don't get any water inside it a VV/VW mod, and don't waterlog a battery in a mech. My main VV/VW is my SVD, which seems pretty well sealed, so unless its an absolute downpour (in which case i'm running anyway, not vaping) i usually don't worry too much about vaping when it's raining. I always wipe the water off when i get inside/to the car out of habit though. But as far as my mechs, as long as the battery doesn't get waterlogged, i dont worry much at all. Hell, i use my mechs in the pool sometimes- if they get splashed or something, big deal, the only thing water can really ruin is the battery. Just wipe it off to make sure nothing rusts/corrodes.
Just my .02