MARTINSVILLE, Va. — Kyle Busch finally figured out Martinsville Speedway in his truck victory on Saturday. He dominated it on Sunday, leading 352 laps and pulling away on a restart with 11 laps to go and outrunning AJ Allmendinger to the finish for his first NASCAR Sprint Cup Series victory on the series’ smallest, oldest oval, and a sweep of the two-race weekend. Busch, who won for the first time in 31 starts at Martinsville in the truck race on Saturday, earned his 35th Cup victory on the season’s first short track.