The BEST teacher is another dog,
That's very true.
Going out on a walk with someone that has a calm and mannerly dog (older dogs are often good candidates) could help a ton. The younger dog will look to the other dog for cues.
My collie was always a lot easier spooked than my other dog, but he'd look to her when he got startled, and being she's scared of absolutely nothing (other than tortoises....yeah...I dunno...
) he was usually calmed by the fact that she had no reaction. It was also a lot easier to train him than her because by the time we got him she already knew a bunch of commands, so when I'd ask her to do something he'd just copy.
Both of these dogs were leash pullers at first, but eventually I could walk both of them several miles and they would stay right by my side the whole time. It just takes a ton of patience. Don't set goals that are too soon. Puppies especially can go through phases and he may actually just snap out of it one day as you work with him.