"Nathan Rissman basically did everything for me," the singer – who produced and narrated the film, I Am Because We Are – told PEOPLE. "He was my gardener. He was my carpenter. He rerouted the electricity in my house. He looked after the children. And he started making home movies of my children. And they were amazing."
Impressed by his work, the singer, 49, tapped Rissman to helm the movie, which documents Madonna's first encounters with David Banda, the boy she has struggled to adopt since 2006. The film is also quite graphic – showing the death of one orphan and the aftermath of another child's violent castration.
"Nathan has the ability to instill trust in people," Madonna said from the stage after Thursday's screening. "And so many of the children started to open up to him ... I've ended up with what I consider to be a very good film and a beautiful son."
Although the film is still in need of a distributor, Rissman said he's honored to be part of the project. "I have to pinch myself all the time," he told PEOPLE.
Life with MadonnaThe Renaissance man also offered a rare glimpse into Madonna's homelife with husband Guy Ritchie and their three kids, Lola, 11, Rocco, 7, and David, now 2. (The adoption process is expected to become final this spring.)
"They're unique parents," he said. "David's walking and talking a little bit now. And Rocco and Lola just absorbed David into the family."