After Awer Mabil opened the scoring in the 23rd minute, Australia's send-off looked set to fizzle into a night of disappointment when Curacao equalised in the 50th, while Ajdin Hrustic (hamstring) had limped off just before halftime.
But Popovic turned to his big guns in Jordy Bos, Riley McGree, Irankunda and Cameron Burgess in the 66th minute and it immediately paid off - with four goals in 17 minutes turning a stalemate into a rout.
"It's a reward because I thought against Cameroon (a 1-0 victory), we could add some more rewards in the final third with a few decisions and movements," Popovic said.Â
"Today, they look a little bit more natural. And then when you get obviously a result of a goal, it confirms what you've been doing, and that should give them a lot of confidence."
After heading one chance over the bar, Irankunda scored a five-minute brace - pulling off a terrific dribble and near-post finish in the 80th minute, then latching onto a Nishan Velupillay ball four minutes later.
After the substitutions, Irankunda and McGree combined before the latter's wicked ball was emphatically headed home by Alessandro Circati - for the defender's first international goal - to restore Australia's lead.
McGree then worked the ball to Bos, who danced through the area and unleashed a superb right foot strike.
Bos then found Irankunda, who beat a defender then fired home at the near post in the 80th minute and backflipped in celebration - then caught a glove thrown to him from the crowd and pulled off Michael Jackson's crotch-grabbing celebration.
Nishan Velupillay slipped through Irankunda to seal his double four minutes later in front of 16,764 fans at AAMI Park, with Popovic hailing the more mature 20-year-old.
"The first one, he dribbles one-on-one, which is great, and the second one, he makes a nice little run in the box," Popovic said.
"So we want that to continue, and that's why I'm delighted for him."
After the 1-0 win over Cameroon, Popovic swung five changes, starting Aziz Behich, Kye Rowles, Kai Trewin, Mabil and Hrustic - while sticking with 18-year-old central defender Lucas Herrington.
It marked Mabil's first start in two years while Trewin was tested in the right wing-back role for the first time.
For the opening goal, Hrustic brilliantly pressed Curacao skipper Leandro Bacuna into a loose pass, with Trewin cutting the ball off, bursting forward then squaring it for Juric.
The striker's flick-on took a deflection into the path of Mabil, who toe-poked home.
In first-half stoppage time, Mabil spurned a golden chance to snag a double when he met a terrific left-footed cross from Hrustic at the back post but volleyed against the woodwork.
Hrustic grabbed at his left hamstring after his cross and was immediately substituted - though Popovic said the playmaker "doesn't think it's anything serious".
Velupillay replaced Hrustic at halftime while Paul Okon-Engstler and Jason Geria took over from Connor Metcalfe and Herrington respectively.
But four minutes later, Arjany Martha was played onside by Geria as he latched onto a ball from Gervane Kastaneer, then burst away from Rowles and scored.
Aiden O'Neill and Mabil spurned good chances before Popovic turned to his bench - and the Socceroos turned the tide.
Once Circati headed Australia back in front, the Socceroos surged to a comprehensive victory.
Australia return to action against Mexico at the Rose Bowl in Los Angeles on May 30.
