I know bashing the OP is a long honored pastime here but there is a nugget of merit here.
As some one with a long family history of heart issues a MI that could incapacitate me while driving is statistically higher then the general population. I always told my children when driving if I become incapacitated shift the car into neutral, don't turn the engine off.
An actual person I know was traveling with her husband driving when he had a medical emergency and slumped over non responsive. Because of the slumping his foot pressed the accelerator to the floor and the car, already highway speed, accelerated. The wife tried to control the direction reaching across the seat but unable to stop the acceleration basically had to pick where they were going to crash. The options were not good, places with people playing, immovable objects like tall trees and concrete barriers, she choose a small pond. The car careened between others and launched over the bank of the pond and sank quickly. She was able to escape but she and bystanders were unable to extract her husband. He passed away at the scene, and because of the circumstances the autopsy was performed and determined he ultimately succumbed by drowning.
I always wondered is she had been told by someone the correct choice in a runaway situation is transmission to neutral would the outcome of that day been different. The mental pain she carried has to be overwhelming.
So why neutral? First it will set your speed trajectory slower, Second you will still have power steering, and power brakes if you can gain access to it, Third some cars passive restraint systems are only active with the key on and you want airbags, seat belt pretensioners and the like to be active, and finally turning the key off may lock the steering wheel and removes options for you.
So not sure you need to practice, but Neutral is the right choice when car is out of control.
And keep you automatic center punch or window breaker in every door ready to break if you end up in the water.