I stood outside and my dad was inside. We showed helped each dog through the door and they all got it. Well kind of. Bear figured out how to go in and out. But he had some issues getting back inside through the doggie door. It was hard for him to push himself up on the ledge and then through the door. But he could do it if he needed to. Otis had a few more issues. If we pushed the door open for him, he would go in and out. But he would not use the door if he had to push it open.
And then there is Lola. She had it down after a couple of times. She loved it so much that she would stand with half of her body inside and half out.
She was content. She could be in both places at once, no matter where the action was.