Your neighbor's way of storing dahlias in a dry box of potting soil is also a method that would work. As long as the tubers do not freeze but stay cool, do not dry out but stay somewhat moist and are allowed to breathe and not get fungal infections. Gardening is an art not a science so different methods work better for different folks depending on their own conditions. Hope your cannas rest peacefully all winter and reward you with fine foliage in the spring. Keep growing, Marianne Binetti