Holy water certainly drives them out, but they come back again. The daily rosary drives them out and keeps them out. It is rather like living in an old house where there are mice everywhere. The only way to get rid of them is to bring cats. If you get a couple of cats, after a week or two there simply will not be any more mice.
Mice fear the very smell of cats.
And in a home where the rosary is said every day, after a time the demons realize they are impotent in front of Our Lady, and go elsewhere. In that home, utterly free of evil spirits, there is an atmosphere one does not find outside. In a demon-infested city like London, where I live, such a home is an oasis of God's grace, and people find a comfort and peace there which they enjoy greatly. We human beings are not meant to live in the company of demons, but with God and with the angels and saints in heaven. So, as I see it, in this effort we are making to keep the faith and pass it on, the practice of the rosary is absolutely indispensable.