What's the best way to start off the line in an automatic
 

Any ideas? Neutral drop? At what rpm? Or hold the brakes with the gas and go?

Best to check with the guys who drag the car for more details, but I believe: pull brake light fuse, stand on brake, launch at desired RPM.

But I honestly get plenty of torque (enough to start going sideways) just flooring it in first.

I wouldn't do a neutral drop unless you want to mess up your tranny and or your carbon fiber driveline.

never do a neutral drop. brake stand is the best 1700 rpm is where i launch at.
you need to have better rear tires or you will just spin them
Mine are 305 35 18 drag radials set at 15 psig.

I would leave the shifter in D, stand on the brake and rev to 2000-2500 rpm and go when you see the last green light. It worked better having the tranny shift for itself at or close to 7000 rpm and avoided over revs if you are late shifting it manually.