Trail braking is the rear brake. That is an important distinction.
Dennis, I know there is a lot of different twists twists to the term "trail braking", but just about all I have read and watched says it is the front brake.
The best way to explain it is shown in the YouTube video below
To back up just a little, what got me looking into this was after looking at comments on another website discussing a crash when a rider was going into a turn "to hot" and all of the factors that come into play in order to correct the line and not cross the yellow line or run off the road.
I also just finished reading a Kindler version book entitled "Cornering Confidence: The Formula for 100% Control in Curves" It wasn't all that great but it did go into using a two-fingered approach to rolling off the throttle with 2 fingers while rolling onto the front brake with the other two fingers going into a turn.
The author also talks about body positioning a bit and I will try it too. We all know that the bike will go where you look, but he also mentions a "kiss the mirror" approach by rotating your upper body some and leaning (probably not the right word) towards it as well.
Don't get me wrong, I'm not trying to say, one way or the other, that braking of any kind is the best way to do things in a turn, but the topic got me curious enough to spend about 2 days researching all I could on the subject.