Jaafar Jackson is making his professional acting debut in just about one of the largest roles imaginable. The 29-year-old newcomer portrays his uncle, pop legend Michael Jackson , in the musical biopic Michael , in theaters Friday, April 24. The film chronicles Michael’s early success both as a member of the Jackson 5 and as a solo artist. In conversation with co-star Miles Teller —who plays Jackson’s lawyer and business manager John Branca—for Interview magazine, Jaafar revealed how he prepared for the role and stepped into the King of Pop’s shoes. “What really helped was having access to Michael’s personal writings. His journaling, his poems, his mantras and affirmations, that was a breaking point for me,” he said. “I started doing the same thing, applying affirmations on walls and mirrors.…