The RAF CFS course taught me that the best way to rotate a stopped engine in flight is to pitch the aircraft hard. It’s to do with the change in the angle of air flow past the blades. Obviously, you need some excess energy in the airframe to do that.
I can recall at least two personal experiences in the Bulldog when the engine stopped during spin training. The prop began rotating again during the recovery (i.e. pitching nose up from the steep descent) once the spin had been stopped. It was by no means uncommon; RAF guidance was to ignore the stopped engine and concentrate on the spin recovery, simply because it might restart itself during the recovery in that way.