Johnson praised the way the new boss has given everyone new confidence.
He said: "He speaks to individuals and has spoken to me about keeping the team's shape.
"He wants it to be perfect because he believes if the team has good shape then we'll score.
"Our shape on Sunday was excellent. They couldn't live with us when we attacked."
Johnson got a hug of approval from Di Canio at the final whistle after scoring Sunderland's stunning second in his best display for the club yet.
The £10million summer signing from Manchester City revealed: "The manager said at the final whistle that this is the start for me.
"That it's going to get better and better for me at Sunderland.
"To score is an amazing feeling, especially against your arch-rivals at their ground. That killed the game.
"It gave me a great feeling to give something to the fans who haven't seen a lot of good football this season."