Cold startup, i turn the fuel shutoff on, crank it over until the oil pressure starts to build, holding the peddle open. Once the oil pressure builds, i flip the switch on, usually the fuel is primed by then, unless you have a weak pump.
Warm fire up i donot close the fuel shut off, because i drive it back to the pits and there's no pressure when the pump is not turning, and will start after a couple revolutions of the motor. If you do close the fuel shutoff and run the lines empty, it will take a little longer to start.
If i were running any nitro at all, even a low percentage, i would definately close the shutoff and run the lines empty and use a couple shots of gas to restart.
JMO
Zip.