well, usually the course of action is to brake hard, then release brakes and maneuver if necessary. Once you achieve 100% traction with braking, steering becomes impossible.

under hard braking of the front wheel, you have to make sure you don't bend your arms because the force of the braking will send you forward. You won't go over the bars unless you actually crash into the bars or shift your weight forward too much.

Rear brakes get useful in sloppy conditions where your front wheel is likely to lock up and skid rather than you endo'ing. Also good in cases where you have a lot of extra weight on the bike where using only the front would likely result in failure of the fork. (surly big dummy readme)

I remember having a coaster brake on a few bikes I've used in the past, but I found them neigh usable. I also figured out that a car can stop way quicker than a bike with rim brakes can.