dog standing facing my left, with my right hand holding the collar and left thumb over the ear flap to pinch when pressure is needed. if you're more comfortable working the other direction, that's okay; do what is most comfortable for you.
holding the dowel/dummy in your left hand, in plain view and close to the dog's mouth, apply ear pressure as you command fetch. when his mouth opens, even a little, slide the dummy in, release ear pressure, and praise the dog. some dogs may turn and open to your hand; if that happens, hold tight, force the dummy into the mouth, then release pressure and praise the dog. the 