I don't like powders at all. They are messy and clouds of powder are bad for the birds respiratory system and you, if you don't use a dust mask. Never use straw either as it only attracts mites and isn't absorbent. I'm glad you went with pine shavings. I dipped my birds once some years ago when I had a bad Northern Fowl Mite outbreak. I made a dip using Ravap E.C.(follow label directions) and dipped all of them up to the base of their necks. Fortunately it was a hot Summer Day and there was no risk of chill. If you have a large flock this time of year it may not be practical. I was tired after dipping 20 birds. In regard to sprays, the only one that I've used with success is Frontline flea and tick spray. It has a residual so you won't have to do it again in 10 days. All you need is a small spritz at the base of the neck, mid back, and below the vent. Be careful not to get it on the vent as it could be irritating to the bird. You might do it a couple other places if the infestation is really bad. Since that time I've followed the rule of thoroughly removing all old shavings, vacuuming, disinfecting, and treating the roosts, nest boxes, floors, and walls with Ravap E.C. or Gardstar E.C. every three months. I've been doing that for 4 years and haven't had a problem since. You need to treat the coop within the same time you treat your birds.