A track technique I learnt some 20 years ago... brake hard when approaching the corner, drop the gear and accelerate hard through the band.
Reason?
1. Changing gears involves a (brief) period of no power to the wheels. If you shift down while the car is slowing anyway, you do not loose-out on forward momentum. If, however, you shift down after the bend when you are ready to accelerate again, you loose a precious fraction of a second when you need it most. So make use of the braking period to have the car prepared in the right gear for the acceleration when coming out of the bend.
2. When you brake, the centre of gravity moves forward, and the weight is off the rear of the car. When you accelerate, the centre of gravity moved backwards and increases the weight on the rear thus holding down the rear wheels. The technique is meant to reduce overseer on RWD cars.
3. Shifting gears while inside the bend is serious no-no, a vehicle is controlled by both braking and accelerating, so having the wheels disconnected from the engine even briefly reduces your control of the car (remember, we are talking track here, not your local Tesco roundabout) and you do not want that to happen mid-corner...
So in short it is brake into the bend, shift down just as you enter the bend, and then accelerate hard through the bend and shift up when redlining in the straight.. Not sure if this is applicable to the road...