Since my daughter is having chickens for the first time, my Dad gave her my Grandma's old nesting boxes, heat lamp and roosts, The roosts have little boxes on the underside of the roost. As the chickens roost, the mites go down and get into the box. You check it to see if the chickens need dusting.
My Dad stopped up today so I asked how old the roosts are. He wasn't sure if Grandma brought them from the other farm when he was little, but they could be from the 1920's. He said they were special made. I got it backwards. Mites feed at night. During the day they hide, so they would use the box. Otherwise, check the bottom of your roost and if you have them, then you dust your chickens and the nesting boxes.