After 60-odd years of driving - most of them automatic cars - I find it almost impossible to drive an automatic using only one foot.
(In NZ, of course, it's the right foot.)
So I use both feet. IMHO, there's no other way to properly control a car if your one foot has to keep hopping from accelerator to brake. For example, backing up a steep, narrow driveway, especially with a loaded trailer. Motorway driving, bumper-to-bumper. Slotting into a sloping, supermarket carpark.
(Ever noticed that most large carparks have their spaces oriented across the slope and not up and down? That's to minimize the mayhem)
So, what's your method? One foot or both?
[Mod edit |Stu| Moved to correct sub-forum.]