Among other things he has edited the journal of the part of Zion's Camp that started in Pontiac, Michigan under the direction of Hyrum Smith.
Between receiving his two degrees from BYU, Manscill was director of the English department in the LDS high school in Fiji.
From 1987 to 1991 Manscill worked in New York City as the director of the Institutes of Religion adjacent to Columbia University and West Point.
Manscill is a co-author of Our Heritage and was on the compiling committee for many of the books in the Teachings of the Presidents of the Church series.
Manscill also served as a historical consultant to Lee Groberg and Heidi Swinton in producing such works as Trail of Hope and American Prophet.