@Jimlaad43 Something I've wondered when I've seen the driver with an extinguisher that the marshal used to have, is: who takes the lead when you have a car that appears to be on fire? I'm guessing the driver has more knowledge of the best place to aim the extinguisher as he has seen the car without bodywork, but I would also imagine that the marshal is better trained and/or experienced. Or is it a joint effort?
If the marshal is confident with a Fire Extinguisher, they are much better to use the extinguisher for the simple reason of we are trained to use them, will have picked the correct extinguisher up and (Tbh the most important part), will be quite excited to finally get to use them. A driver may be aware of where the fire is coming from, but they aren't necessarily trained to fight a fire. A small fire can be put out with one properly aimed squirt of Powder by someone who knows what they're doing, whereas a driver could panic and just empty half the bottle in the airbox, damaging the engine and not putting the fire out.
Good bottle usage is a squirt for a few seconds, let the dust clear so you can see what the effect is and then go again when you see what the result it. You need training to understand how to use it properly.
When I'm marshalling, the most a driver will do with a fire extinguisher in their hands is get the pin out for me while I climb over the barrier and no more. They have flameproof clothes on and adrenaline, which can cause dangerous over-confidence or lack of danger awareness in relation to being close to fire.
Fernando didn't pick up a bottle and let the guys put the fire out for him, Vettel stole the bottle and fought it himself. My priority for the drivers is that they're safe and not burning, so get out and stay away. You have the kit on to run back in and turn the electrics off if required, don't burn your kit doing something else.
So yeah, I wanna use the bottle, don't be a driver who steals my fun.