In order to speed up the evangelistic process, it is good to have members of a missionary team who are from a culture that is similar to that of the target people. A team can save many years' work in this way. After there are more converts, team members who are culturally more distant can be effective in discipling them behind the scenes. Missionaries need to learn to cooperate with team members from other cultures. Some areas in the unevangelised world have been under Satan's sway for hundreds or thousands of years.
Much prayer is required to see a breakthrough.
The Holy Spirit led the Lord Jesus into the desert to fast and overcome the evil one. It was only after this victory that the Lord began His public ministry. Not only that but all the way through His life, He spent long periods in prayer, cast out demons and preached the Good News in the face of much opposition. His holy life and obedience to God meant that the evil one had no authority over Him. Missionaries need training in godly living under pressure, and in spiritual warfare.