But it is fellow painter and documentary filmmaker Ross Brodar, whom Montiglio credits with "turning my life around," who pushed him to paint, sometimes up to 12 hours a day.
A former all-star lacrosse player from suburban Long Island, Brodar had his own demons.
He was a "troubled" teenager, stealing cars, and spent ages 16 to 19 in a court-ordered therapeutic community. There, in a tough love setting among drug addicts and criminals, he discovered painting through art therapy.
"I believe art is therapy for people like me and Dom," Brodar, now 38, told ABCNews.com. "It's a need to express pain, hope, death and fear without words, just color, line and emotion."
The two met at a gallery in 2000 and for two years sold their paintings from a 26-foot parked van, snubbed by the annual Outsider Art Fair.
Eventually, fair director Smith and the Netherlands-based Olof Gallery took notice of Brodar and then Montiglio.
"I knew I was going to be friends with him," said Brodar of Montiglio, who was invited this year. "Something about him is different and his work really interesting," said Brodar.
"I took Dom into my home and studio, and in exchange for room and board, he gave me his life story."
And what a story. Montiglio was so "high up" in the mob he went to New Year's Eve parties at the home of Paul "Big Pauly" Castellano, who as head of the Gambino family was gunned down outside a Manhattan restaurant in 1985 on orders from John Gotti.
His tyrannical uncle threatened to kill Montiglio's father if he ever tried to make contact with his son.
"He chased my father away. The biggest wound was after I finally tracked my father down, he was dead already," said Montiglio, who was 27 at the time. "You can't talk to the dead."
The pressure Montiglio felt to join the mob was described in the 1992 book, "Murder Machine" by New York Daily News reporters Gene Mustain and Jerry Capeci.
As a first grader, the boy was told he couldn't be a policeman and as a popular teen, Montiglio was forbidden to serve as class president because it involved keeping track of troublesome classmates.
"No one in our family can be a rat," he said. "Basically, I was like Nino's robot. Whatever he said, I did."
A football player, he was ridiculed for an interest in art in high school, but was allowed to play saxophone and sang in a doo-wop band, The Four Directions.
But his uncle refused to support Montiglio's music career: "It's okay to blow somebody's car, but not to sing," he told his nephew. Gaggi also opposed military service, but Montiglio joined anyway.
After returning injured from Vietnam in 1968, Montiglio became deeply involved with the DeMeo crew -- and the life.
With a single phone call, he could get nine front-row tickets to a Tom Jones concert in Las Vegas, but there were also the brutal killings -- worse than anything he had seen in Vietnam.
"Every Friday night we'd chop up the money," he said. "When I walked they were at the kitchen table eating spaghetti, and the door was ajar in the bathroom with two bodies hanging naked and bleeding out. Who were these guys? I'd say, 'Don't worry, I'm not staying for dinner.'"