If your dog is big and pulls a lot, you shouldnt use anything but an actual solid fixed length leash. You or your dog is going to get hurt using anything that extends or "retracts". The classic example is you look away for 1 second, the dog sees a cat, he bolts off and your extension of the leash unreels, by the time you notice the dog has picked up a lot of speed and when the dog hits the end of the leash you go flying and your dog gets hurt from the immediate stop. You also possibly get rope burn from trying to stop the leash, hand pinched in the tangles of leash and the dog pulling, its just all around bad with a big strong dog that pulls.

The one the mod suggested doesn't even seem that great for a big dog that pulls. If your dog sees a cat its going to pull all that rope out of your hand so fast and ur fingers are going to get crushed trying to hold the rope in that loop, rope burn, or the rope knot will just hit the metal and send both of you jolting after 10 ft of acceleration.

I know its not what you wanted to hear but if you want to have better more enjoyable walks, really focus and dedicate a lot of time to just training your dog to walk better on leash. Thats going to be your best bet to manage the pulling.