Hi GJO,
Your 9 month old is trying to visit, but also wanting to establish some type of dominance order. There's all sorts of reasons for it, but the behavior comes down to not being acceptable or wanted by you.
Have you tried using a Halti style head harness at all? My small dog, Chienne, had the same trouble as your dog. She'd want to visit, but then she'd snap if they got too close. (passive agressive wishy washiness :rolleyes: ).
Anyway, using the head harness, I was able to keep her face towards me while we were walking by or another dog coming over to sniff her and our other dog. She didn't like the "Stand" and take it order that I gave her, but she learned that snapping is not acceptable.
Now she's much better, even when she's only on her regular collar. She'll moan, but no longer the high pitch crazy barking and out of control self that I had been dealing with for her first 4 years of life ;)
I like the fact that the dog looks at you when you want it too. You keep track of where the mouth and eyes are. Looking away (for a dog) defuses tense situations. Just remember, if you try this to be very gentle. It is direct pressure and does not require much strength to use use it. Chienne being only about 18 pounds, I just use fingertips and not the hand/arm leverage that I needed on a regular leash.
good luck with your puppy :)
toodles