He also translated LDS Church materials into Spanish, wrote magazine articles, and spoke regularly at general conference.

When Rey was nine, the Pratts moved to Mexico to help settle Colonia Dublán, a Mormon colony in the northern state of Chihuahua.

Shortly after serious fighting began in Mexico City in 1913, the church's First Presidency authorized the Pratts and the American missionaries to return to the United States.

Two years later, the First Presidency again instructed the Pratts to move, this time to Manassa, Colorado, and establish missionary work among Mexicans in the United States.

He continued to expand the mission, opening up work in southern California in 1924 and establishing a Los Angeles branch.

Pratt's duties expanded further in January 1925, when church leaders called him to be a member of the seven-man First Council of the Seventy.

Grant announced that apostle Melvin J. Ballard and Rulon S. Wells, another seventy, would go with Pratt to establish the LDS Church in South America.

The Voltaire stopped in Barbados, Rio de Janeiro and Montevideo en route to Buenos Aires, Argentina.

Pratt returned from South America to find Mexico caught up in another internal war, this time over the issue of separation of church and state.

Just after the April 1931 General Conference, Pratt stayed in Salt Lake City to undergo a hernia operation.