Rooney, who scored twice in the 3-2 San Siro victory that put United in such a commanding position, weighed in with two more at Old Trafford as United swept into the Champions League quarter-finals to stay on course for a third successive final.
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Park, who will line up for South Korea at the World Cup starting in June, scored the third with a rare goal after an hour - having briefly taken a break from his completely effective man-marking job on Andrea Pirlo - and Darren Fletcher put the icing on the cake with a late header.
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"It was a fantastic night for us," Ferguson told reporters. "Wayne Rooney's performance was just a continuation of his performances for the last two or three months, just sensational, unbelievable.
"The key tonight was Park and Rooney. Park played a game of sacrifice with discipline and intelligence that won us the game."
Rooney opened the scoring with another powerful header after 13 minutes to swing the tie heavily United's way and Ferguson said his practice at that discipline had paid off.
"His movement in the box has improved this season, he's practiced a lot more, he does heading sessions after training and I think you get your rewards," he said.
The striker, upon whom England's World Cup hopes rest, then showed lung-bursting ambition to be first to Nani's cross a minute into the second, bringing lavish praise from Milan coach Leonardo.
"I think that Rooney is still young but he is a very complete player, he's fast, strong and scores a lot of goals," said the Brazilian.
"He's fast over short and long distances, he's a very, very good player and is playing in a system that for him is perfect. On the counter-attack, he's incredible."
Leonardo said the damage in the tie had been done in the first leg and with his team suffering more injuries ahead of Wednesday's game they faced a virtually impossible task.
"It was always going to be hard after losing the first leg and conceding a goal so early made our comeback even more difficult," he said.
"But one thing we can't deny is the powerful and strong performance United put in. "We met a team who are in extremely good form."
