You speak it and the Spirit wields it. The Word of God, that is. God reminded me again about 3 weeks ago how important it is for me to be speaking out the Word of God as I pray for my family (or anyone or anything, for that matter!). The Word of God is part of the armor of God. It's called the Sword of the Spirit. If it's a sword and the only offensive weapon, it's pretty important in our battle against the enemy. The impressive thing is that we don't have the hard part of the battle. All we have to do is speak out the Word. The Spirit has the strength, power, and precision to wield the sword.
I can tell you that I've seen dramatic results as I've prayed/spoken the Word of God aloud. It's not enough just to read it--even though that is necessary and important. Reading the Word transforms our minds. But Satan can't read your mind. It's when you speak the Word that power is loosed. A sword is put into the Spirit's hand to use in battle. I'm convinced.
Try it. Come in agreement with God's Word for your situations. Pray it aloud. Give the Holy Spirit a sword to use. And let me know if it makes a difference.