I'm about halfway through American Moses, my March 2005 Book o' Month. Much of Brigham Young's early story parallels the path of early LDS history (New York to Ohio and Missouri, then Illinois), so in this comment I'll highlight a less familiar episode from that period, Brigham's mission to England in 1840-41.
When Brigham Young stepped off the Patrick Henry onto the Liverpool dock on April 6, 1840, he no doubt experienced the relief of getting back onto solid ground, but also anxiety in the face of the immense challenge of preaching (with few resources) a fledgling religion in a foreign land. England had been sending preachers and missionaries to America for two centuries; sending Americans to proselyte in England must have seemed nothing short of unnatural to many Englishmen, an offense to the established order of things.
That thought never seems to have deterred Brigham or his fellow Mormon apostles, who converted about 5,000 people over the next year. By 1870, close to 40,000 converts had emigrated to Utah, and thousands more remained in England. What explains the success of Mormon missionaries and Brigham in England?
First, Brigham didn't screw up. Many first-time leaders simply never grow into a leadership role, and proceed to alienate subordinates, miss opportunities, and squander resources. Brigham did things right: he had a low-key, self-effacing style that won him friends, not enemies; he took the message to the folks who were interested in hearing it and lost no time in organizing English congregations of believers; and he generated resources to support needed activities in publishing and building. It was Brigham's game to win or lose, and he came through marvelously.
Second, he had good help from fellow Mormon apostles such as Parley and Orson Pratt, Heber C. Kimball, Wilford Woodruff, and Willard Richards. Leading men of the United Brethren, a Herefordshire group of Primitive Methodists who joined the Church in large numbers, were quickly made into local LDS leaders, and the new Mormon congregations full of English laborers flourished. As for Brigham, himself a laborer from humble circumstances, his "simple, direct preaching was effective." He spoke their language, if with a Yankee accent.
Third, he didn't just convert people or even just establish congregations, he built Mormonism. By early 1841, Brigham had printed 3,000 hymnals (already featuring several unique LDS hymns) and 5,000 copies of the Book of Mormon. The LDS periodical The Millenial Star was being published by mid-1840, delivering up-to-date news of the Church to the new English converts, as well as selections from the Book of Mormon, messages from Brigham Young and other LDS leaders in England, and letters of support and encouragement from that distant American, Joseph Smith. Mormonism also meant gathering, and ships full of Mormon converts were heading off to America almost as soon as people started joining up.
Fourth, and possibly the most important success factor, there were whole congregations seemingly just waiting for the Mormon message. As Sidney Rigdon and his congregation of Disciples swelled the Church in New York in 1831, so did John Benbow and Thomas Kington and their United Brethren (like Rigdon's, another Christian Primitivist movement) boost the Church in England in 1840. To these scattered or loosely affiliated congregations, the Mormons supplied an institutional matrix of leadership, hierarchy, and vision. The congregations had bodies and (some) capital; the Mormons brought an exciting (religious) business plan. Result: a successful (religious) enterprise, a missionary success story.
Brigham and most of the apostles returned to the US after about a year, with Parley Pratt staying behind to run LDS affairs in England. Brigham was back in Nauvoo by July 1841. His next big adventure lay west, not east; across the prairie and over the mountains, not across an ocean.