Greenwood scored a well-taken opener in the 16th minute with Bruno Fernandes scoring the other two as United impressed on the south coast.
With United now up to fifth in the Premier League table following back-to-back league wins, Solskjaer was particularly pleased with Greenwood and has praised his attacking threat.
"Mason's first goal was brilliant and he played fantastically," Solskjaer told Sky Sports.
"He's a special kid, we know when he gets faced up he looks dangerous. His link up play was great today.
"He's got a knack of that, he can go inside or outside, he is developing into a fine player. We know we have pace and we want to counter quickly, it was a fantastic goal [the third goal], we are very happy with it.
I don't care about making a statement, I know we are a good team. We will recover and then focus on the next one.
Potter: We go to Norwich to fight
Brighton can take a major step towards securing survival if they beat the league's bottom side Norwich City at Carrow Road on Saturday lunchtime.
It is a game their boss Graham Potter is extra keen to take all three points from following the home defeat to United.
He told Sky Sports: "We got killed on the counter-attack for the third goal but we had some good play but against United you are always on the stretch. It is a tough evening for us but one we will take a lot from and learn from it.
"We always look at ourselves to try and improve and they are as good as anyone we have played this year. It is hard to contain but a positive performance in the second half.
"We knew before the game where we are at and the fight we have got, that does not change anything. We go to Norwich to fight."