I propose that the conversion of Ireland (and the closely linked conversion of Scotland by the Irish) are textbook exemplars of how evangelism ought to be carried out. If we take the example of Patrick lighting the Paschal fire on the Hill of Tara, we see that Christianity was introduced as something over and against the prevailing religious systems. On one hill, the light of the druidic priests was lit, but the Paschal fire on another, to symbolize the light of Christ coming into the land darkened by druidic error. They were not the same light, but two opposing lights on two opposing hills. Whether or not the stories of Patrick's often miraculous conflicts with the druids are historical, in them we see a man who viewed his God as being against the gods of the heathen, who were evil spirits. Patrick would never have confused people by trying to show how Lugh and Jesus were actually the same god; he confronted paganism when he saw it.
The confrontations were always in the spirit of charity; Patrick won over every king and ruler he met by his gentle demeanor and honest character. But he harbored no doubt that the gods he contended with were false, and his contests with the druids demonstrate this. For example, when the druids caused it to snow, and then Patrick, in the name of God, made the snow go away, we see the understanding that the gods of the heathen were either (a) nonexistent, or (b) malevolent spirits hostile to the true God. Like St. Benedict with the famous altar of Apollo, Patrick once destroyed a large boulder that was being worshipped. His God was the Lord of Hosts, Who loved the Irish people but detested the abominations into which they had plunged themselves. However much Patrick loved the Irish, he never thought twice about destroying their idols.
Furthermore, Patrick understood the best means to win over people. As he went about baptizing and ordaining bishops, he did not leave behind ecclesiastical institutions but founded monasteries. Patrick and the Irish conversion demonstrates the long held conventional wisdom of the Church that those committed to the religious life are the best persons fit to bring the Gospel to the new lands. By their vows, their simplicity of life and their humble servitude, they bear witness to the truth of Christ's Gospel and lead others to follow Him. All of the early Irish saints are monks, all of them famous for setting up monasteries (like St. Columba on Iona) and all of them viewed monasticism as the best way to Christian perfection.