The AAMI Park match could hardly have started worse for PNG, with their Brisbane Broncos fullback David Mead knocked out in the opening set while trying to tackle halfback Luke Gale.
Scored six minutes apart, McGillvary's tries were strikingly similar with the athletic flanker reaping the rewards of a sweeping England backline move, although credit for the second must go centre Kallum Watkins who delivered a special backhand flick pass.
The Kumuls blew their only real first-half chance when centre Kato Ottio dropped a soaring bomb in the in-goal with his team trailing 14-0 at the break.
England extended that to 20-0 in the 56th minute with Ben Currie running on to a neat grubber from fullback Gareth Widdop, who was on target with the conversion.
But the crowd of 10,563 were on their feet soon after when PNG winger Garry Lo etched his team's first points with a try in the corner.
England continued to dominate despite their mounting error rate and the willingness of the Kumuls to attack, with Watkins showing his skills to bank two tries and winger Ryan Hall then adding the closer in the final minute.