Red Mite question

Have just got back into chickens after a few years break, gave up mainly because of foxes- I used to free range them. Missed them terribly and have made the decision they have to stay in runs.
Dont have any red mites yet, I dont think, have been spraying with poultryshield once a week when I clean them out and dusted the birds.
Just read on another forum that Detol is just as good and spraying regularly will kill mites and not hurt the chickens.
Obviously the cost of Poultryshield is a lot for routine spraying. Has anyone used Detol and does it work?
I am paranoid about mites after some of the posts I have read so would welcome any advice on prevention.
BJ