When you say he goes ballistic when he sees another dog is it with excitement?
Aswel as integrating them together you will have plenty of work in general to discipline the new dog. On the disciplining method side I remember before I moved out of home we had a husky pup. She was an absolute nightmare to begin with. Every night she would howl non stop and she would destroy the place downstairs, let’s just say she wasn’t getting the whole house training thing. She was my mother’s dog and my mother went to a vet in swords who we always use and asked had he any advice. There was no question of ever physically disciplining any dog we ever had, my mother treats them like her own kids (not always a good thing).
He told her of one sure way he knew of to show a dog wrong from right without slapping them on the nose. It was to sit on the stairs at night and wait for the dog to howl, have a rolled up news paper and every time the dog howled to to go into the room and smack the paper off your hand a few times in front of the dog. Apparently the noise frightens the shite out of them. After about two weeks of this the howling and shiting everywhere just stopped. In fact the dog became one of the most easily manageable dogs we ever had. Walks off the lead beside us, house trained and not an aggressive bone in its body all thaught through the newspaper method. It took some preserverance at first but it was worth it.
Have done this with my own dogs too and worked a treat. We’d a problem with the lurcher diving up on people when they came into our house. The method we used for this was to have a spray can of water and spray the dog in the face with the water. It’s harmless and just annoys them. After a while doing that the OTT welcomes people got had stopped.