Performance vehicles are usually modified (if necessary) so that the heights of the brake and accelerator pedals are closely matched and the pedals are not too far apart, to permit easy use of heel-and-toe.
The name, stemming from earlier automotive designs where the accelerator pedal was on the left and could be actuated with the heel while the brake pedal was actuated with the toe, is misleading regarding how the technique is carried out in modern cars, i.e., operating the brake with the left edge of the foot, while rocking it down and to the right to operate the throttle. With practice, it becomes possible to smoothly and independently operate both pedals with one foot. The technique is common in all forms of motorsport, especially rallying.
As the power band of most rally cars is high in the rev range, this technique can also be used to ensure that engine rpm does not drop below the power band of the car while under braking. If this happened there would be a delay between the driver accelerating after the corner and when the car responds; this is especially true in turbocharged cars. This technique ensures that maximum power can be reached the instant the brake pedal is released and the accelerator fully depressed.
When a driver performs a heel-and-toe downshift, they will first use the ball of their right foot (toe) to depress the brake pedal and slow the car down sufficiently. When the car is at the appropriate speed, the driver fully depresses the clutch pedal, cutting the power from the engine to the gearbox, and now shifts to neutral.
After that, the driver releases the clutch and rotates their right foot to operate the throttle with the outside edge of their foot (heel), increasing the engine speed to match the required rpm for the selected gear. Then, the clutch pedal is depressed and the correct gear selected from neutral, the clutch again released, and the engine connects to the gearbox once again.
Finally, the driver places the right foot back onto the accelerator, releasing the brakes.
On cars where the brake and accelerator pedals are very close together (as is the case with many racing cars), it is not necessary to rotate or twist the foot: the (right) edge of it may be used to "blip" the throttle, with the ball of the foot being suitably offset on the brake pedal.
It is worth noting that shifting to neutral may not be necessary. The driver can blip the throttle when the clutch pedal is depressed, then shift to the lower gear and release the clutch. While a modern synchronized transmission does not require double clutch shifting, a driver may choose to perform it in order to lessen wear on the synchronizer.
Utilizing natural human body mechanics, an alternate heel-and-toe technique can be used. In this method, the right foot is splayed out, with the heel control the brake pedal, while the ball of the feet near the little toe control the accelerator. It is much easier to rotate the toes from the feet outwards away from each other than the reverse, the feet can flex much more from the ankle, while the braking can be modulated by flexing the knee giving a much more extended range of control for the brake and accelerator pedal.
With practice, one can quite easily apply, modulate and hold the duration of braking and engine revolution as often, or as far and long as wished simultaneously. The flexibility of this method, apart from sporty driving, can be quite useful for creeping or stop-starts on up or down steep slope from a dead stop with total control and finesse. One simply flex the right toes for exact amount of engine revolution, ease off the clutch with the left foot at the same time as relieving the pressure on the brake pedal under the right heel and move off. No hand/parking brake assist is ever necessary, and with virtually no rolling of vehicle.