Learn to Use Two Fingers
One way to help refine the trail braking technique is to use two fingers on the front brake. This allows the use of both the brake and the throttle, which is useful for transitioning smoothly between braking and acceleration. The advantage of two-finger braking is that it allows the two remaining digits to remain on the throttle grip (usually the ring and pinkie). This is useful when implementing advanced throttle/brake techniques such as brake and throttle overlapping or throttle blipping.
I comfortably use both, 1 finger (on average speed cornering / trail braking) 2 fingers (on traffic filtering) for better throttle blipping when down shifting gears.