"Trail" braking is not a reference to the rear brake; it refers to "trailing off the brakes" as you enter a corner. Trailing=smooth, slow release of the brake lever as opposed to "flicking" the lever loose.
Rear brakes "should" be used in conjunction with the front, but this is a very, very debated topic. Lots of MotoGP riders don't even use their rear brakes. Others, "back it in" (intentionally causing the rear tire to slide) to aide in getting the bike pointed in a very acute angle more quickly. There are other techniques of rear brake while in the corner to again, help steer the bike's direction plus offer some extra safety while leaned but reducing the speed.
But the front brake is critical to stopping and should be engaged proportionally to the throttle (throttle off, brakes on, brake off, throttle on). Throttle chopping cause the bike to become unbalanced whereas braking causes the bike's mass to transfer reliably. That is why you "trail off" the front brake to move weight from front-to-rear in the corner and be in position to throttle out of a corner.
It is my experience that despite decades of riding, many of us probably do some of these things innately, but we might also do them poorly. I always marvel at how much better I ride after some these track training sessions. Whether it's reminding myself, or being more conscious of what I am doing, or simply that you spend time on a track riding well beyond the limits of the street and gaining comfort, competence or experience at 50* lean angles at 60+ MPH and realizing the bike can do it. Something you might never likely try on the street due to safety and legal reasons.
It honestly also taught me how critical good suspension is to raise the confidence bar. I personally believe tires and suspension deliver more speed, control and safety than anything else on a bike. Brakes are surely important, but traction is everything in my book.
