The Killie boss was also quick to praise some of his player's individual displays, singling out Robbie Muirhead and Gregg Kiltie for plaudits.
"It was a real team performance but there was also some really good individual performances," PA quotes him as saying.
"Robbie Muirhead was great, while young Gregg Kiltie was fantastic too starting his first game. He took the ball in tight spaces and was never afraid to play a pass."
Johnston went on to praise the influence of experienced squad members Kris Boyd and Sammy Clingan, insisting that the club cannot afford to lose the former.
"The young players did so well but without the experience of Boydy and Sammy Clingan that result wouldn't have been possible. We cannot afford to lose somebody like Boydy. He is too big a player for us with his goals," he added.
The result moves Killie up to eighth in the table.