I think good riders can ride with or without braking in curves. Generally IMO it's better to practice the following drills (not necessarily in this order, but #4 is definitely last):
1. Ride your favorite twisty road without the brakes, using engine braking to set your corner entry speed (for most riders, especially new riders, this will require a lower gear than he's used to).
2. Ride your favorite twisty road in one gear, without shifting, but practice using the brakes smoothly for speed control as necessary.
3. Ride your favorite twisty road in one gear, without shifting, and without brakes.
4. If you can do all that smoothly, you will find that you can now go faster if you shift frequently and use the brakes, but this results in a pace that is basically insane on the street. On my bikes ground clearance is enough of an issue that a faster pace leads to hard parts dragging and scary moments where the rear tire loses touch with the pavement. So I don't push it any farther. But I can't quite master #3 anyway.