Spiritual ministry isn't dependent upon technique. It's the outflow of a way of life.
The moment we adopt the "technique" approach in Christian work we are little better than witchdoctors trying to manipulate higher powers. That might sound extreme, and perhaps it is. Nevertheless, whenever we try to gain the influence of another realm through rituals or techniques, we are engaging in a kind of shamanism. And that's not the way we enjoy the presence of the Holy Spirit working in and through us. He will not be manipulated.
Indeed, he is absolutely sovereign in the exercise of his power. Ultimately there is nothing we can do to ensure that his power attends our activities for Christ. We can, however, be assured of his presence if we live humble, dependent lives. Jesus has promised to be with his disciples until the job of discipling the nations is done (Matthew 28:20). From that point of view we don't need to do anything to gain his presence - he is already with us and living in us by his Spirit if we truly belong to him.
What we need to do is to "walk in the Spirit" rather than in the sinful nature (or flesh). Anyone who does that, seeking to integrate their lives into the spiritual kingdom of God, can be assured that the Spirit will work in and through them as he pleases. They will never be abandoned and left to their own resources if they fully trust in him.
That's the key to effective spiritual ministry - if there is such a thing as a "key."