Here's how I do it.. Keep the toes of your right foot on the brake (medium pressure) and with your right heel rev the gas pedal to around 4~5K, dump the clutch with the left foot. The second you dump the clutch you will need to modulate the gas and the brake with the heel and toes of your right foot. Once you get used to it it's easy. Once the tires are spinning fast in the water box you can usually move your right foot over to the gas and put your left foot back on the brake. You barely have to touch the brake in the water box after every thing is spinning, but will need to apply more brake as you come out into the dry pavement.
Don't even try it on the street unless it's cold out and it's the right kind of pavement. You know, that shiny slick pavement.