The person who appears to Daniel in chapter 10 is an unnamed angel - a messenger not Jesus. Michael the Archangel,(Good name there!) is mentioned as assisting him, and while angels attended to Jesus, they would not have been needed to tip the scales in a fight. Jesus would have only needed to speak a word, and the demons would be bound.
Daniel is aware that he must be in prayer and fasting, but the connection to Michael is unknown.
What we do know, from verses 12 - 14 is this:
Then he continued, “Do not be afraid, Daniel. Since the first day that you set your mind to gain understanding and to humble yourself before your God, your words were heard, and I have come in response to them. But the prince of the Persian kingdom resisted me twenty-one days. Then Michael, one of the chief princes, came to help me, because I was detained there with the king of Persia. Now I have come to explain to you what will happen to your people in the future, for the vision concerns a time yet to come.
Since we know that the Devil is "the prince of the power of the air," and that there "powers and principalities" in the demonic realm. Many have suggested that each ethne (a people group or nation-state) has their corresponding demonic prince. If that is the case, then what delays Michael is this demonic ruler of the Persian peoples, preventing the prophet from receiving the message.
We know this can't be a human detaining the angel, because either an angel or a demon could easily overpower a human - clearly there is some demonic force preventing the angelos from delivering his message.
So, was it needed for Daniel to be fasting the whole time? In so far as Daniel's praying and fasting was a perquisite for the dream, we can safely say No, because:
a. There is no evidence that human prayer affects angels in any way (Angels are merely messengers of God)
b. There is no evidence that God requires prayers to work some magic - to assume otherwise is to make God contingent upon us. While it may get God's attention, it does not compel him to act or in any way affect his ability to effect what he desired. Having gotten his attention, God dispatches Michael to clear the impasse
c. There is evidence that demons are subdued in the power of Jesus's name, but not that we are responsible. (In Acts 19:15, the demons admit they know Jesus, and know of Paul - but they are completely baffled by some people who think they can control the demons speaking.)
Why then was Daniel was it important for Daniel to attend to prayer and fasting then?
The simple answer is, it was preparing Daniel for the message, even as Michael is being detained.