All electric motor brakes are is when your ESC deliberately shorts the motor against itself, causing the motor to take the kinetic energy of your car and use it to generate electrical current that is disippated as heat through the windings of your motor. The braking force your motor/esc combo can provide is proportional to the RPM it is turning, so when the motor speed approaches zero (which can easily happen in a slow apex) the braking force goes to zero. This is why in a car you can be hard on the brakes but still roll another six feet at walking speed (my 1/12 does this real bad). All ESC's and motors do this.
As far as driving fast and consistent goes while being on the brakes, I try to have markers where I hit the brakes and let off again.
For everything else, I tend to run a few laps at a set throttle position, and just hit the lines, and slowly speed up until I hit the lines at wide open and I know the car is feeling right.