Always driven manual cars since the age of 17, I'm now 51. Four years ago I got my first automatic which was a Mercedes with the selector on the right hand stalk, with the indicator on the left stalk. My problem was not so much the clutch, it was going down to look for gear lever.
Since getting my Vellfire, I now have a habit of turning indicators on to move it into drive, and putting the wipers when I turn. I will get used to is soon/
With regards to left foot braking, unless you are racing and need quick reaction to break and accelerate, don't do it. If you have been driving a manual car then you have trained you left leg to depress the clutch pedal all the way down. When you use your left foot, you may have a habit of breaking harder then you need, and I can't really see the need to risk this when you have been taught to use right foot for break and accelerator and never had a problem. Maybe countries that only really have automatics teach this way.