sounds like a handful - but fun!

there are a number of good books out that can help with reactivity; it does not matter what the root is, over-arousal, frustration, aggro, whatever, each of them can be re-trained with DS/CC - desensitization + counter-conditioning.

* Click to Calm - excellent book, theory + background in the front, literal step by step recipes for coping and B-Mod in the back. many of my clients have had good success using this, all on their own.

* Control Un-leashed:
another goodie - Look at That! is a technique that rather than having U react by pulling the leash tight + stop breathing when U see/hear another dog, which only cues the dog to react, instead U cheerfully announce, Look at That! a dog... and start paying out treats as fast as the dog can swallow. (if the dog cannot focus enuf to eat the treats, or if s/he is actually barking, U are too close - back-up a bit, and U can keep feeding while fading back, as long as s/he will eat them.)

the local library may have one or the other - if not, try Interlibrary Loan.

by *treats* i mean SMALL but extremely high-value, low-fat items - not biscuits!
tuna bits from a pouch, grated-low-at-mozzarella, meat-based cat-kibble, anything that is stinky, tiny, and very-very Good. each tidbit should be no more than 1/4 inch cube, and preferably less - an 1/8 inch is fine.
i have also used salmon-bits mixed into low-fat cream-cheese, organic yogurt (vanilla),
and other messy stuff the dog must LICK, not bite - which keeps them very busy! i use a camping-squeeze-tube for the gooey stuff.

keeping the dog UNDER threshold during the B-Mod process is important - meaning Not barking, lunging, etc. so U need to work in an area with lo-o-o-ng sight-lines, so that U and the dog are not caught by surprise with a dog coming out from between parked cars right in front of U. and preferably there should be NO loose dogs - so a parking-lot near a pet-supply with a stream of dogs arriving at a distance is perfect. a block away from the dog-park, with dogs passing by as U sit under a tree off the walkway, is another.
sitting within sight + sound of the vets office is a good one!

i would skip introductions on leash until he has largely got past the barking + lunging - giving him a possible opp to practice the Un-Wanted behavior is very if-fy.
Practice makes Permanent! is a training mantra.

cheers, and happy B-Mod!
--- terry

terry pride, APDT-Aus, apdt#1827, CVA, IPDTA, TDF