Poor baby indeed! You might have to have help getting it fitted the first time, it's important that it fit him sortof snug so it stays right up under his jaw at the top of his neck, and not down on the strong muscled part of his neck.
Perhaps his first lesson needs to be sitting still to get collars and leashes on. It can't stay on him all the time so you need to be able to do it every time you walk him or work with him.
If you could look into his face, you would say poor baby, too. My mother says he is a horse and is not really a house dog, but she says "poor Harm" all the time. My poor baby is not welcome to visit anyone. :( Mama tries, but she is afraid she will fall over him he is so big. He does not jump on her. He seems to sense if people, children or adults, are fragile.
Yes, putting on leashes and collars should be our first lesson. That is one of the most difficult things I have to do with him. He also pulls out of his collar and it is so hard to get it back on. He has done that in the vet's office and run around the waiting room causing all kinds of havoc.