For much of his career Kyle Busch has been the most talented driver on the track since he burst onto the scene as a 19-year-old NASCAR Cup Series pole-sitter in 2005. Lately there are days Busch isn’t the top wheelman in the house. Brexton Busch, his 6-year-old son, is winning at a clip that Dad envies a bit yet also uses for inspiration and insight into his own craft. As last Sunday’s runner-up during Busch Light Clash exhibition race at the Los Angeles Memorial Coliseum, Kyle Busch had hoped to piggyback his son’s dirt-track victory the previous night in South Carolina. “I was trying to matc…