My advice to people who start to learn trail-braking is to pay attention to how weight shifts. First find a safe corner free of walls and try braking about 20-40% (to be safer) and then start smoothly turn the wheel, assuming it's left turn, and feel how weight moves from front end to the right front and then to the right as you release brake pressure. As you turn wheel and weight shifts you can feel suspension being loaded (springs are compressed) to front right side- it's a great feeling as it's loaded and ready for 'action.' From that you can manipulate the vector (direction and amount) of the weight by both brake and steering inputs to see how car reacts and find limits. Eventually it can be done from higher braking pressure, higher speed..and (maybe..) where walls are close.
Key is careful, incremental experiments and feel of and smoothness in weight transfer. Then.. brake pedal from throttle pedal transition should (be smooth enough to) maintain how weight is loaded as before beginning track out of the corner.
If an instructor is not quite happy with your smoothness, most likely you are not smooth enough. Sometimes it may feel like you are doing smooth enough for what you do and they sound like a bit too much (for even their driving pace); but as you get faster and faster, YOU will need that smoothness eventually.
