My first instructor who was a former BoB pilot who said he saw many pilots trying to blow out flames by diving. Never worked.
Under discussion he made the suggestion to slow to the stall to stop the prop and stop feeding the fire with fuel and oil.
Have demonstrated this several times at height overhead the airfield.
Pull mixture and show the trainee the prop doesn't stop, until close to stall speed. Then have restarted the engine (yes I have done a few power off landings, bit silly looking back but nice to know what it feels like).
Reminds them the need to warm engine, just to check it's still running normally.