what about the emergency brake? I would think that the e-brake in combination with even a semi-failing pedal brake would be enough to slow down to a non-fatal speed.
That is the last brake you want to touch in that situation. It does not have the braking power that the normal brake has (less than 1/2 the braking power) and it makes the car unstable at speed, making it more likely to spin out or swap ends.
I won’t go into detail about how to do boot-leg turns, but it does involve using the emergency brake. Boot-leg turns are the turns you see on the movies where a car is going full speed forward then suddenly spins around while sliding sideways and then faces the opposite direction and heads off in the opposite direction.