And it proved the perfect send-off for 63-year-old Smith, who has landed an impressive 21 trophies for the club including 10 SPL titles.
"The lads who have been working with me - Ally McCoist, Kenny McDowell and Ian Durrant - have been patiently waiting for an opportunity to take over," explained Smith.
"I think they thought they would possibly get it a bit earlier but they haven't and they have been fantastic for me. That was part of my decision and it was the right one."
Asked where this achievement ranked with all his others at Rangers, Smith added: "I don't think you can pick and choose.
“I don't think we were the favoured team this season and the boys have fought extremely hard”
Walter SmithRangers manager
"If you have won a few you are fortunate to be able to try to answer that question. Each one of them are special for you."
Rangers knew victory at Rugby Park would secure the silverware regardless of events at Celtic Park.
And the match was all but over as a contest after seven minutes.
Kyle Lafferty grabbed the opener after only 47 seconds, before Steven Naismith netted and Lafferty found the back of the net again in a blistering opening sequence.
Nikica Jelavic fired in a free kick after the restart and Lafferty completed his hat-trick before James Dayton netted a consolation goal for Kilmarnock.
"We had a fantastic start and the standard of finishing for the first three goals was exceptional," said a delighted Smith.
"It was a terrific way to start and eased the nerves a bit.
Media conference - Walter Smith
"If you look at the games we have played since the defeat by Dundee United [on 2 April], we have been playing some good football.
"We have started the last half-dozen or so games well and we did that today. To be 3-0 up after seven minutes is something we never expected. It was a pleasing factor - it just leaves you more than 80 minutes of the game to handle."
Celtic pushed Rangers all the way in a topsy-turvy title contest and Smith added that he had enjoyed the tussle with his old rivals.
"If you look at the seasons, a lot of them have been like that in recent years," he added. "When that's the situation you are in, it's always interesting.
"Somebody said to me the other day that Celtic lost the league at Inverness but they didn't because they lost other games as well and so did we.
"Whatever happens, it's not just one particular game that causes you to lose the championship.
"For us, it's been a really good one. I don't think we were the favoured team this season and the boys have fought extremely hard."
Smith's assistant, McCoist, will take over as manager for next season and was quick to praise the outgoing Smith.
"I thought the quality of goals we scored were outstanding at any level," said McCoist.
"Most of all, Walter Smith deserved it today. His record is absolutely outstanding and the way he conducts himself as a manager - he's a top human being."
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