The power of demons
Satan is a created being, and therefore can only be one place at a time. That's why he has MANY servants (demons). Their job is to seduce believers away from God.
If you are afraid of them, or attribute them (or their lord) as having more power than they actually have, they will use that. If you have God the Holy Spirit in you, they are terrified of you. They should be! For you have been given the authority, by your relationship with God through Jesus Christ, to not only resist them, but cast them away. Our friend from Japan was right in that it doesn't take some "certification" to battle evil.
In the book of Acts however, there were seven brothers (the sons of Sceva) who had witnessed Paul casting out demons in the Name of Jesus. When they tried it, declaring the demons leave in the name of jesus that Paul preached, the demons replied: "Jesus, we know, and Paul, we know; but who are you?" The demons then attacked and destroyed the brothers. What these men lacked was the authority to act in the Name of someone they did not personally know. The Name of Jesus is not some magical mantra that just anyone can wield to make things happen. It is the gift of great power given to those who know Jesus personally. That is the only requirement to command the demons.
If you don't have that personal relationship and are not filled with the Holy Ghost, you should NEVER attempt confronting demons. You are unarmed and have no authority against them.
I agree that the Body of Christ needs sound knowledge about our enemy. Hollywood makes him and his hordes seem far more powerful than they actually are.
I love the true story from the life of Smith Wigglesworth, a great man of God. One night, he heard loud crashing downstairs in his home, waking him. He went downstairs to see what was happening, expecting to find a robber. The intruder he came face-to-face with was not a demon, but Satan himself, standing there in Wigglesworth's living room. Satan had been ransacking the place, trying to disturb and terrify Smith. Smith Wigglesworth looked at the beautiful creature standing before him (remember that Lucifer was the most beautiful angel God had created, and the Bible does not say anything about his appearance changing. He appears as "an angel of light") and said, "Oh, its just you" and went back to bed. If we don't let evil intimidate us, then it can't. If we not only declare his impotence, but truly believe it, then the devil has no power over us at all.
Just one more comment: We should carry Scripture in our hearts and minds, ready in an instant to answer temptation with the Word. Its what our Lord did when He was tempted in the wilderness.
Be encouraged and do not fear!