Boult was declared Man-of-the-Match for his two for 21 in six overs while Southee took two for 35 in his eight overs as they reduced Scotland to 12 for four inside five overs and eventually bowled them out for 142.
"They are world-class bowlers (Boult, Southee) and they have stood up for a long time in Test cricket for us. It is outstanding when you are able to win the toss, choose to bowl, and then be backed up," McCullum said after the match.
"Credit to them (Scotland) for posting a good total that was tricky on this kind of surface. I am pleased with the result in the end, but we definitely showed nerves towards the end. We will take the result, and points from the game. Really good performance with the ball and in the field, but we need to improve on our batting," he said.
New Zealand take on England next on Friday in Wellington and for McCullum "it will be a great challenge" but he was confident of a good show.