First, welcome to the obsession! I am not sure sugar dusting would be as effective as spraying with sugar/water solution in preventing the bees from flying (which is mostly why it's done, not as a food source for the bees) just the wetting action alone makes it harder for them to fly. Also, note that confectioners sugar is not the same as powdered sugar (confectioners sugar contains corn starch and other ingredients that you do not want your bees eating, it can be very hard to find powdered sugar). Lastly, do your hives have screened bottom boards? Because if they don't, the mites will just crawl back up to bees when they are knocked off.