I really value positive training and use it whenever possible to help teach the dog new skills. I have found it great for obedience and puppy training but I question its value with advanced retriever training (though retriever training is inherently positive - as long as there's a bird at the end of every retrieve). I also don't think there is such a thing as 100% positive.
With that said, I think you can train a decent or even nice gundog able to do multiples and blinds without the use of force or aversives. Below are a couple of folks I know about who try to take a "purely positive" approach.
Lindsay Ridgeway (mentioned above):
and Robert Milner