i am not sure, but i don't think you can ever expect smokey to go off of insulin while he is eating dry food. it all has a lot of carbs, even the lowest dry formulas - i'm not expert on that, but that's what i understand. if smokey has concurrent health reasons that have caused you to keep him on dry food there might be other ways to address those issues while still giving the canned food.
just seems like you've got a great opportunity here that with a change to the right canned food, he might not need injected insulin. my understanding is that once a cat has been diabetic you must always continue to feed them the low-carb canned food. returning to their previous non-diabetic diet will likely mean a return of the active diabetes and injected insulin.
i don't mean to go on about it, denne', but sometimes people don't know. if you know all of this and still want to do it, that's your choice, of course. you might send a pm to one of the more experienced people and ask for their input on the topic.