I was told by my mentor 27 years ago if someone tells me that in order to train a peak that I would need a 2x4 my response would be "No, you just have to be smarter than the dog"!
Chesapeakes are self thinkers and guard dogs. Had to be....if not, they weren't around very long.
Not so much soft, you just need to be fair and to teach.
Like Tim Carrion says, you negotiate with a Chesapeake.
Also, socialize,socialize, socialize.....what time you put into your pup is what you will get out of your pup.( this is for all dogs, not just a peake)