I have done this lots of times, and the best tip I can give you is that you need to try to carry as much speed as possible through corners, dont brake hard then expect to accelerate out of bends, it wont happen, karts dont have enough torgue to do that, but, when the tyres are nice and hot, they do have the grip to go round bends faster than you might think, so, you can take lots of people coming out of bends as they bog down and have to wait for their karts to get going again.