When it comes to doing the double by racing in the Indianapolis 500 and the Coca-Cola 600, no one's done it better than Tony Stewart, the only driver to ever complete all 1,100 miles in both races on the same day.

In 1999, Indiana native Stewart finished ninth at the Brickyard and fourth at Charlotte Motor Speedway. Two years later, he had lead-lap finishes in both races, coming home sixth at Indy and third at Charlotte.

So if anyone understands what Kurt Busch is facing on Sunday as he attempts the double it's Stewart -- who just happens to be co-owner of Busch's NASCAR team.

Stewart, who came up through the open-wheel ranks, said the largest hurdle will come in the first half of the Indy 500, which will be Busch's first race in an IndyCar.

"Those experiences that happen during race day -- you can talk to somebody and you can tell him how bad it's going to be at the start of the race," Stewart said. "I guarantee it's going to feel worse to him (Busch) than what we even can describe it to him. It's little things like that -- when you're a fan and you watch the 500 and watch the start on TV, you have no idea how turbulent the air is, you have no idea how bad the fumes are. Your eyes are watering because of the fumes. It's tough and demanding."

The speeds and the strategy make the 500 a much different race than anything Busch has experienced in NASCAR, according to Stewart.

"It's not just about who has the fastest car, but you have to plan way ahead with everything that you do in the car," Stewart said. "A pass sometimes starts three-quarters of a lap earlier than when you actually make the move. Those are things that are different than what you would see in a Sprint Cup car. You can tell him, but until he gets in that situation and experiences it firsthand, he's not going to understand until he gets in that moment."

Stewart said advancements in IndyCar technology since the days he raced there will make for a daunting challenge for Busch.

"I think it's going to be tougher than what most people are going to give him credit for," Stewart said. "They think you're just going to get in there and you're going to drive a racecar. And you don't have to learn how to drive a racecar. There's a lot of work that you do -- clicking buttons, shifting gears on the paddle shift, weight jackers, fuel maps that you're changing -- there's a lot of things that an IndyCar driver does other than just drive the car. ... A lot of that you just can't teach somebody until the race happens and he gets in those scenarios will he understand it. He will have a strong foundation before he gets to the race, for sure, but there's a lot to learn in a short amount of time."