[tenderfoot]

In other words he is great if it suits him.

He is in the habit of bolting when he sees other dogs. Thats his habit and it has worked for him. Stopping might work in certain situations but you need to stop the thought before it becomes and action and get his mind busy and on you.

I would work on your speed of interruption. for a while you should try to change what you are doing with him every 5-10 steps. Changes direction, speed, stop, TURN INTO HIM a lot. As much as you can don't use the leash just your body language. Of course you have the leash on but try not to use it unless you have to. In the beginning you might need it a lot but then see if he will cue to your voice or body. Exaggerate your actions so that he can cue in. i.e. when you stop scuff your foot loudly and stop abruptly.

If you can stop the thought before it becomes an action then you are changing his habits and preventing the adrenalin rush that comes with going after other dogs.

The micro-second he sees another dog - when he first raises his brow or twitches an ear - you cut right into his shoulder and do a 180 turn into him. Walk away - work on drills - be a bigger distraction than the other dog. Each time you head towards the other dog you should be able to get 2 steps closer. Progress. Soon you will be able to walk past the other dog with no lunging. Don't forget to reinforce the 'leave it' command if he starts towards that dog.