Have a little riding crop in your "neck rein" hand. As you apply pressure on his neck with the rein, the riding crop should move up beside his face (don't wack him accidently) and just sort of jiggle it there beside his eye.
My mare would have absolutely flipped if I waved a crop in her face!]
You aren't "waving" it in her face, I said just a little jiggle, or in some cases, just a touch to the cheek and she would move away from it.
My Anglo is a very hot mare, and she took it very well.