Lardy says something in his videos like "the worst mistake an owner can make is doing nothing because they didn't want to mess the dog up before getting them to the pro."
Not to argue with you or Lardy (for crying out loud!), but if I remember the story right, Rex Carr once stated that he'd like to have a 6 month old puppy that nobody had messed with. So, the Belmonts raised a Lab that was even allowed to sleep in the fireplace; ashes and all! That pup grew up to be the famed multiple National titled Super Chief!!!
Not saying that is the best way to do it, but it didn't work out too badly in that case.