Prayer is the most potent spiritual procedure. Fasting may help as preparation for prayer, but there isn’t always time for it.
I have experienced cases where verbally commanding a spirit to leave didn’t work, but it was expelled by prayer.
I’m not sure why you are mincing words, but what is the difference between commanding a spirit to leave in the name of Jesus (which is the only authority by which you could do so) — or a prayer?
I’m sure the Lord knew what He was saying when He instructed the disciples that they needed to fast and pray for the spirit to leave. Why is this an issue for you?