The Australian left-arm fast bowler collected four wickets for 41 runs, as West Indies, replying to the Aussies' first innings total of 251, were dismissed for 216 on the second day of the Test at Kensington Oval.
Johnson had arrived in the Caribbean with a growing reputation, but he failed to make a lasting impression, and could only snare five wickets in the previous two Tests in Jamaica and Antigua.
After another wayward opening spell in the morning session on Friday, Johnson recovered to flatten the bottom half of the West Indies' batting in a purposeful spell after tea to give Australia a lift.
"I was a little bit more relaxed after tea," he told reporters. "I was probably forcing it a little too much in the morning.
"It's just with how my tour has been going - I have not been getting too many wickets - I sort of just felt that I really needed to get some wickets in the morning and probably just forced it a little bit too much.
"But I had a few of the boys just calm me down a little bit, and I guess after the wicket (of Dwayne Bravo) I just felt really relaxed, put a big smile on my face, and I guess that is how I performed at my best."
Bravo was caught down the leg-side by wicketkeeper Brad Haddin for 29 to open the floodgate which saw West Indies collapse dramatically after tea under the weight of Johnson's spell.
"I haven't really thought about my form on tour too much because I don't think I have bowled badly, but I haven't been at my best either," he said.
"Test match cricket is a very hard game, and sometimes it goes your way, and sometimes it doesn't. Hopefully, it has turned around at the end of the tour for me, but better late than never."
Johnson had been relegated from the role of new-ball bowler from the second innings in the opening Test in Jamaica, leaving Brett Lee and Stuart Clark to do the business with the new ball.
But Johnson believes he is more comfortable bowling an older ball, since he has had more practice performing in that role.
"There has been a lot of talk about me with the new ball and swinging it and that kind of thing," he said. "I seem to find that I am a lot more comfortable when the ball is a little older at the moment.
"With the new ball, I try and swing the ball, and that is not how I play my game. I sort of hit the deck hard and get it through. When I get that new ball in my hand, I am trying to swing it, rather than hit the deck like I normally do.
"I think I am just going to keep working on hitting the deck hard, and working the ball through. Hopefully, I will get another chance with the new ball again, we have another innings so we will see what happens.
"But I guess I have been doing this - bowling first change - for a while now and I am probably a little more comfortable. I haven't opened the bowling a lot, so I definitely would like that new ball.
"There is nothing better than bowling with the new ball and opening with Brett Lee for your country, so I am definitely going to be working on it and get better at it, so that I can hopefully terrorise top-order batsmen with Brett."
Johnson, who is playing in his ninth Test, acknowledged the biggest lesson he has learnt from the tour is the need for greater patience with his bowling.
"I wanted to be patient this tour, and I probably haven't been as patient as I've wanted to be," he said.
"This first innings, the first spell, was probably the least patient I've been.That was due to probably not having too many wickets. I was trying to take a wicket with every ball, trying to bowl the perfect ball.
"There have probably been glimpses of it in the other games as well when I've tried to get wickets every ball, but then I've got back into being patient and hitting the deck and the right areas.
"This is my ninth Test. I'm still learning the game, and hopefully, I can keep growing. It's a tough game and I want to be around for a long time."
Australia continue on Saturday's third day from their bedtime total of 35 without loss - a lead of 70.