"The way the wrecks happened and the restarts, we were just in the right line at the right time and we were able to pull it out," Hamlin said Thursday night, calling the win a confidence boost.
He will enter the Sprint Cup race Saturday night 17th in points with just one top-10 finish after eight races, and that's 15 spots behind where he finished last season.
Busch had dominated all night, but when the race went back to green after a caution with three laps to go, Hamlin surged from fourth to second right away, stalked his teammate with Joe Gibbs Racing and passed him on the backstretch when Busch ran out of fuel.
"I'm glad he ran out of fuel because it might have got ugly," Hamlin said. "Trust me, if Kyle wouldn't have run out of gas, I would have done everything possible to get around him."
Hamlin, who said last week that the race raised over $100,000 last year, said he will wait to see how much money was raised this year, then give 10 percent to help tornado victims. Where that money will go specifically will be determined by where there is the most need, he said.
His usual charities -- the Cystic Fibrosis Foundation, St. Jude Children's Hospital and Children's Hospital in Richmond -- will receive the other 90 percent of money raised.
The victory was the first for Hamlin in his fourth Short Track Showdown, and came after he qualified on the pole, then opted to start at the back of the 36-car field.
When it was over, he gave his racing helmet to a fan.
"He had a 48 [Jimmie Johnson] shirt on. I figured he needed an 11 helmet," he said.
A crash on a restart with 10 laps to go helped Hamlin move from eighth to fourth on the grid, and when he bolted to second on the last restart, Busch's fuel problem finished the rally.
Waltrip said he never considered trying to nudge Hamlin aside for the victory.
"How can you knock a guy out of the way when it's his race?" he said.
After starting 36th, Hamlin moved up to 16th after just 15 laps. He was up to eighth when the race paused for a planned caution after 47 laps -- a 5-minute break during which the teams were allowed to take only two new tires and make adjustments to their machines.
For Hamlin, still being in contention was a stroke of good fortune. On the opening lap of the race, a crash in front of him caused him to spin, and he was able to avoid crashing.
The race was held for the first three years at Southside Speedway in Midlothian, a Richmond suburb. It was forced to find a new home when the local track, where Hamlin refined his racing craft in Late Model cars, did not open at the start of the season because of an illness.
The move to Richmond, with 100,000 seats as opposed to the 4,000 or so seats at Southside, and SPEED's plan to televise the race on cable made it likely that the exposure for Hamlin's event would increase exponentially, but rain held the walk-up crowd down significantly.
The track did not announce the attendance, but only a few thousand fans braved the rain.
The Blue Ox 100 NASCAR K&N Pro Series East race, which preceeded Hamlin's event, had run just 29 of 100 laps when it was delayed for nearly 2 hours by heavy rain and lightning.
That pushed the starting time of the Short Track Showdown back more than 90 minutes.
In the Pro Series East race, Wallace won, outrunning Brett Moffitt.