What do you think of Holy Water?
Jesus never said to resort to that for casting out devils.
Matthew 17:18 And Jesus rebuked the devil; and he departed out of him: and the child was cured from that very hour. 19 Then came the disciples to Jesus apart, and said, Why could not we cast him out? 20 And Jesus said unto them,
Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you.
21 Howbeit this kind goeth not out but by prayer and fasting.
I see prayer as submitting to God the task and fasting is denying you have any part in it. Jesus Christ will cast them out.
John 14:13 And whatsoever ye shall ask in my name, that will I do, that the Father may be glorified in the Son. 14 If ye shall ask any thing in my name, I will do it.
We may even need His help to believe that if anyone has doubts in those perilous moment.
Mark 9:23 Jesus said unto him, If thou canst believe, all things are possible to him that believeth. 24 And straightway the father of the child cried out, and said with tears, Lord, I believe; help thou mine unbelief. 25 When Jesus saw that the people came running together, he rebuked the foul spirit, saying unto him, Thou dumb and deaf spirit, I charge thee, come out of him, and enter no more into him.