I think mixing it with actual dirt decreases the dustiness somewhat. It's what I did last winter and it worked out much better than straight wood ash.So far I only put ash in one area outside and not tons of it. I kind-of let them decide if they want to use the ash area or a different area. That way I'm not locking them in to using the ash if it is irritating or such.
ETA: Last winter I had some inside too. I DEFINITELY understand the indoor dust storm syndrome.
I thought wood ash + water makes Lye? That can create chemical burns on your chickens. Which is why I never had any outside (except the basic camp fire area).
I don't bother with it outside, as most of the chickens dust bathe on the forest floor.