Lukaku was instrumental for the Red Devils as Brazil’s defence struggled to contain the Manchester United's pace, power and movement for most of the game.
The 25-year-old, who had previously worked with Martinez at Everton, explained to the media
"I have played in this system more often at Everton (the former club of Lukaku and Martinez), and I knew exactly what to do.
"I helped Eden Hazard and Kevin De Bruyne and explained to them how they should stand and what to do, explaining once was enough, we did the job perfectly, we won deservedly."
Despite failing to find the net himself, Lukaku was a constant thorn in the Brazilian defence's side. Although he admitted that he wants to score as often as possible, the former Chelsea striker pointed out that improving the play of his teammates is just as important.
"My all-round game is always my strong point, I try to make other players better, I want to score as much as possible and also give as many assists as possible, and I am very busy with the team, so I can be important too."
The victory means Belgium will play their first World Cup semi-final since 1986, where they will take on Didier Deschamps' France in St Petersburg on July 10.