My new coop ~ dry dry dry ~ and new shavings ~ dry dry dry ~ have been dusty too. I added DE a few weeks after getting everything set up for the new girls and it didn't seem any more dusty so I sorta' thought it was the shavings. We'll mist the horse stalls sometimes when they get really dry and dusty just enough to moisten the shavings but I'm worried to do that in the coop. I'd rather it be a little dusty than moldy and mildewy!
seriously, you don't *need* it. If you just feel you gotta have some in there to discourage future mite infestations, put it *under* the bedding not mixed in or on top, and only use a little bit, dusted into crevices.
Yes, deep accumulated litter in some climates and/or with some particular bedding lots *can* get dusty - I'd suggest playing it by ear, do what seems sensible to you based on your particular situation.
I did not have De this winter to use and I still had very deep poultry dust on everything. I actually took a shop vac. and cleanned it several times because of the dust. I now have DE. I am using it for the fly, odor, mite prevention and to keep it dry. I really don't think it matters. gloria Jean