When driving any manual or F1 car I shift into neutral and keep it there while I'm waiting for the time to go. If I am still rolling and the light changes, just use either paddle and you will get a gear. Whether that is the 'official' way or not, I really don't care. It works for me and I am very easy on clutches. I also manually downshift, rather than let the car do it. If you want long clutch, just don't slip the clutch.