either - do the shut off from an idle setting.
If the carb is correctly adjusted and all is in good repair - restarts should be a flip -or two.
IF the engine was very warm when shut off - restart may require choking again as the carb simply boils off the gas .
IF the idle needle (low speed fuel needle ) is too lean -restarts will be difficult.
Most gassers - when properly set - will instantly restart from a normal temp run - after say - 10 minutes.
The initial engine runup may hesitate slightly till temp reaches operating levels.
We have checked this on our ownengines as well as many other setups done by competition flyers - at TOC etc..
Never throw a rag in the prop.
I remember a fool who demonstrated this technique years back as his clever method.