I'll try to explain it a little better.
1. Press the brake pedal down pretty hard with your LEFT foot. You don't have to do it really hard, but just enough to keep your car from moving.
2. Apply the gas (right foot, obviously) to whatever RPM you want to launch at. After tests, I have concluded that my GT wont rev past 3000rpm, even after its all the way to the floor. Usually a launch is between 1800-2300rpm.
note, don't hold down the brake torque for too long. This causes a TON of stress on the whole drivetrain, and heat builds up quick.
3. Launch: Release the brake pedal quickly and keep your gas pedal foot in the same position as the launch, then accelerate progressively. This is where the practice is. Floor it too quick, you can break loose and have absolutely no traction. Floor it too slow, well, you get a bad launch and your reaction time and whole ET are effected. You want it so your tires are just barely gripping with the power you're feeding them.
did i do ok?