Yes, this should help to kill the little vampires. Maybe he can pick up some cans of cheap dog food and a dewormer on his way. Dog food is a good source for protein and vitamins.. And when the chicken have mites they surely catched worms, too. Mites are one of the things everyone get sooner or later and they are a pain not only for the chickens, but also for the owner who has to do all the cleaning and dusting. Often our chickens catch them from wild birds. they are living taxis for worms and mites, so maybe you can help the wild birds, too, and build a cat-safe bathtub for them too deworm and demite them. In pet stores you can find bathadditives for exotic birds that are great but are not allowed for chickens.