Heel toe does what the game does for you in sequential mode.
The purpose of Heel toe in REAL life is so you can downshift while braking while keeping the car stable and taking advantage of engine braking to assist you in slowing the car.
If you downshift WITHOUT heel toe, The clutch, and the flywheel are rotating at different speeds..and when they MESH , it shocks the drive line as the clutch has to "drag" the engine up to the appropriate RPM to match wheel speed. This wears out your clutch, and will most likely upset traction.
By Using Heel and toe, You are matching the engine rpms to the wheel speed, while shifting, while braking. all at the same time.
In the game, using sequential and automatic and AUTO CLUTCH..The game does this for you..So you dont recognize the need for it. It is a very handy tool for use in real life.
You also dont need to go through each gear...You Can simply brake...Wait untill you reach the appropriate corner entry speed... Rev match to the gear you WANT using heel and toe, Then go directly to that gear and go