The Rugby Park side pinched ninth place in the Scottish Premiership table from Saturday's opponents despite being dominated for large spells.
But his boss was just delighted to see his team come through a difficult afternoon with a victory after seeing their efforts go without reward on a number of other occasions this season.
The Killie manager said: "It was a massive game for us and you could see we were a bit edgy. It wasn't our best performance and Thistle played really well.
"It's actually nice to get the three points when we haven't played well because it's happened to us numerous times this season when the other side has struggled.
"Hopefully that is now us turning the corner and we can build on this result. Looking at the league table, it's really tight and it's massive what a couple of wins can do."
Johnston planted the ball past Thistle keeper Scott Fox four minutes before the break after both sides had struggled for fluency in the opening half.
The lead last just four minutes into the second period, though, until Doolan dummied Jereon Tesselaar before wrong-footing Craig Samson in the away goal with a cool finish.
The Jags should have come up with a second equaliser though but watched in horror as Stevie Lawless blazed over from just five yards out.
He paid the price for that miss as Boyd - who overtook Celtic icon Henrik Larsson's league goals tally with his strike against Dundee United last week - got another crucial touch to Irvine's low drive on 70 minutes to take his tally for the season to nine.
Yet it was Craig Samson who was named man of the match by the sponsors as he produced saves against Kallum Higginbotham, Ross Forbes and John Baird late on to preserve Killie's win.
"Everyone will be talking about young Chrissy Johnston getting himself another goal and Craig Slater and all our other young boys doing well again," said boss Johnston. "But I thought it was the two old boys who stole the show - Kris Boyd and Craig Samson.
"Boydy was in the right place at the right time once again and that's why he has overtaken Larsson's record. As for Sammy, he was unbelievable with some fantastic saves. That's why he has been in the Scotland set-up."
Higginbotham's miss while one-on-one with the keeper was another bitter pill to swallow for Jags boss Alan Archibald after he was forced to watch Lawless' gaffe through his fingers.
"The chances we missed cost us," he said. "They were two massive opportunities and they don't come much easier than that.
"Stevie knows he should have taken the chance and Higginbotham is the same, although in fairness to him Samson has made a great save and come out and spread himself well.
"It cost us, especially with Stevie's one, because they went straight up the park and scored.
"It feels like we were robbed. To come to Rugby Park and dominate the play but not get the points is disappointing. But I've been saying that all season long - in this league, you must take your chances."