Laidlaw had been stationed at fly-half for much of the season with his club side.
But he was moved back to his more natural number nine slot by Johnson prior to the RBS 6 Nations championship getting under way following the retirement of record-breaking half-back Mike Blair.
On Sunday, he justified the boss' decision when he kicked all 12 points and marshalled a forward pack that stood up magnificently to a first-half Irish onslaught that somehow failed to break through to score, despite Declan Kidney's men at one point racking up possession stats nearing 80 per cent.
Glasgow loosehead prop Grant was one of those forwards who defended for his life in that opening 40 minutes, setting the foundation for the 12-8 win which moves the Scots into joint second in the Six Nations table.
But he hailed the kicking and organisational display of Laidlaw following his four perfect penalties.
He told Press Association Sport: "Greig is a class, class player. He is great with the boot and a great marshal of the pack.
"That's why he's perfect for the nine role. He speaks to the forwards and lets us know where we need to be.
"He does the same with the backs and has got a great understanding with them."
Scotland ridded themselves of two nagging 12-year problems as they beat Ireland on home soil in the championship for the first time since 2001.
The victory, which followed the 34-10 triumph over Italy earlier this month, was also their first back-to-back success since that same campaign.
Grant feels the team's rivals will now have to change the way they think about Scotland.
He said: "We did acknowledge that there was a perception of `Same Old Scotland` who will, you know, win one, lose one. That kind of thing.
"So we wanted to stamp that out and show we are not a one-trick pony. We wanted to put consecutive results together."
Asked if a title push was a realistic proposition, Grant added: "Yeah, sure. Anything is possible now. It's an open tournament now.
"But by no means was that our best game. We have got a lot to work on before the Wales game."
Johnson explained after Sunday's match that he opted against ranting and raving at his shell-shocked players following their sub-standard display in the opening half.
Instead he gave them a calm appraisal of where they were going wrong and Grant insisted the boss had got it right with his assessment.
He said: "It was a game of two halves really. In the first half we were under a lot of pressure and defended for a lot of it.
"That shows a lot of character from the boys that we were able to withstand that for the first 40 minutes.
"We didn't get any possession at all and we needed to get out on the front foot and keep hold of the ball at set-pieces, so Scott put an emphasis on that.
"He wanted much of the same in defence - just to keep them out - and the rewards would come.
"Ireland had a lot of possession but I can't comment on their game plan or what they were trying to achieve.
"But we spoke about line speed before the game and trying to shut Ireland down, especially in and around the ruck and I thought we did that well.
"A lot of it came down to the forward pack and defending in and around the ruck area, which is where they attack a lot.
"We were unable to unleash our back three, which we would have hoped to do if we`d had more possession.
"But that's part and parcel of the game and you take what comes with the territory."
Meanwhile, Scotland hooker Ross Ford should be fit to face Wales in a fortnight despite having to have his face patched up following the side`s RBS 6 Nations win over Ireland.
The Edinburgh front-row forward retired early in the second-half of yesterday's 12-8 victory over Ireland at Murrayfield after picking up a facial injury.
But the Scots` medical team say the stitched-up 66-time capped player will have his part to play when the Welsh visit Murrayfield on Saturday, March 9.
Scotland team doctor James Robson said: "Fordy suffered severe facial lacerations, we believe as a result of a collision or collisions.
"Ross was treated at Murrayfield, then one of our matchday doctors, Gerry Haggerty, took him to St John's Hospital in Livingston, where he was cared for by one of their plastic surgery specialists.
"He received multiple stitches to the wound and was able to return to the team hotel last night.
"Our expectation is that with ongoing good care and attention to the wound, Ross should be available for consideration for the Scotland v Wales game."
The Scotland medical staff, Dr Robson and physiotherapists Paul McGinley and Stephen Mutch, will continue to assess the remainder of the squad over the next 24 hours.
However, Dr Robson added: "Despite the rigours of yesterday's Test match, the rest of the squad appears in rude health today. As usual, they will continue to be medically monitored over the next few days."