I use my left foot for all braking in an auto.Suprisingly easy to get used to modulating your braking imput ,even in an emergency situation.I started many ,many years ago when I owned a Humber Super Snipe auto which refused to idle, so keeping it running whilst braking required both feet - one on the brake and one on the throttle to stop the thing from stalling.The habit has stuck to this day.
There's a Heel-and-Toe technique for that, which is a must in track cars as they are all manual, but the accelerator and brake pedals have to be at the same level for this.
Basically you twist your right foot inwards, keep the toes on the brake pedal and the heel on the accelerator, this allows you to brake and accelerate at the same time.
Just in case is sound too loony (why would you want to brake and accelerate at the same time?), you don't do this while the clutch is engaged, instead you do this when you change gears midcorenr - it allows you to rev up the engine before popping the clutch, while slowing-down through the bend. You need to develop some feel to operate the accelerator with the heel which is less sensitive than the front of the foot, but other than that it works a charm.