Turn off VDC, put it in M-mode in first gear, hold the footbrake and raise the revs just a little (2K-ish or less), then side-step the brake and roll into the gas pedal smoothly and quickly and manage traction with the pedal and the steering wheel. Also, don't hold with that footbrake for too long, just a second or two. If you hold it long you'll quickly overheat the fluid. 2nd gear pulls pretty hard, it's better to make the mistake of shifting to 2nd a little early than to wait a fraction of a second too late and bump into the soft rev-limiter at the top of 1st (which you'll reach very very quickly, and you have to keep the 7AT's shift input lag in mind...).
But really, who cares about first gear? Drag racing a car just puts a bunch of unnecessary stress on the drivetrain. All the real fun happens in 3rd-5th gears and involves frequent cornering and braking
