In all honesty, in the early days I tried to go easy on him and focussed on just 5 mins pavement type walking then straight into a field for off lead. I don't know whether that helped or hindered me. What I have now is a dog as described on the lead but pretty brilliant off lead (certainly more so than some of his gun breed peers).
I stopped still in degrees, so at first it was only the really hard pulling I would stop for, gradually lowering my threshold to be increasingly sensitive to pulling. Even today I will 'excuse' some slight pulling without stopping, in the spirit of keeping walks fun and upbeat. In some ways, the dog enjoying his walks and having fun were the most important factor for me, more so than polite lead walking.
I always tried to take advantage of the right behaviour and would walk quickly or even trot for loose lead so we made up our time then.
He learned to slacken the lead himself when we stop very quickly. That bit was easy, so even if we have lots of stops I know he will get us walking again after a few seconds by moving back to me to loosen the lead.
Sometimes I wonder if mine pulls in groups still because they are the times I was/am less inclined to stop still - just because it disrupts the walk so much. One suggestion (that I never could get organised enough to do) is to have 2 different lead combinations...
e.g. a harness that you never expect him to loose lead walk on, allowing you to have more social walks in the early days then a collar/lead in which you work on loose lead. The idea being that as he slowly learns you use the collar combo more and more until it is your default. That way the dog has a clear signal between having fun and walking by your side.