Hi,
I don't know much about Supras (yet) but I do know a bit about autos...
The fastest way to launch is to put the box in "drive" (or "1" if you're gonna use manual mode), your left foot hard on the brake, and your right foot about 1/4 of the way down on the throttle. This should work especially well on the Supra as this should get one of the turbos spinning ready for action Then when you want to go you floor the throttle and sidestep the brake simultaneously. Of course, depending on your traction control this can result in a lot of smoking tyres, so try it a few times to see just how far down you need to put your right foot before launch, and how quickly you need to floor it.
As has been mentioned above, this isn't something you really want to be doing except at the drag strip, as it's usually not great for the car. You should be able to get nearly the same speed by leaving it in "Drive", holding the brake with your right foot just lightly enough to stop you creeping forwards, and then letting go and flooring the throttle when you want to go. Again, dilute to taste depending on how much traction you're getting.
Thunking the car from neutral into Drive at high revs is not a good thing.
Hope this helps!