trail braking is simply still applying the brakes after you've started to
turn in to the corner.
You are probably already doing this in gpl without really realizing it. If
not, then you are braking in a straight line, releasing the brakes, and then
turning in.
you can carry more speed into the corner (brake later) by easing off the
brakes as you start to ease into the steering in such a way that the two
braking forces (turning the wheel of a car causes some braking) equal the
max. grip you have. as you turn in more, you let off the brake more, so
that the two added braking forces always add up to 100% of your grip
(ideally).
example: straight line: 100% brakes, 0% steering
start to turn 90% brakes, 10% steering
turn more 70% brakes, 30% steering
etc. etc. etc. (by steering I meant percentage of braking
caused by steering input)
hope that made sense ( i doubt it did),
speedracer