The important thing to remember -- if you're not comfortable with it, don't do it.
We don't advocate folks going out and doing this in traffic for the first time. It takes practice and getting to know your vehicle first, then implementing techniques and practices.
Having an automatic, I can't take they key out unless it's in Park.
I have performed an emergency stop with the engine off. Vehicles generally have one good pump before the pedal gets stiff. I always turn the key back to the "On" position, which engages the ABS. Antilock brakes work fine on my car with the engine off.
I'm one of those 50-lb pressure guys: but I insist on high quality tires and inspections.
Bottom line: I'm a safer driver because of this philosophy. I used to be a road-raged idiot and performance driver. Hypermiling has slowed me down, and mellowed me out.
And for that, I give thanks to everyone along the way who has changed my life for the better
Best FE to ya...
RH77