How does one brake while drifting with the Nunchuck controls?
With that controller setup, you can't. Kind of a bummer because it's the same one I use. The problem is that with a wiimote + nunchuck setup, B means "drift" when you are holding down the accelerator, and "brake" when you are not. But in order to brake-drift, you need to be holding down the accelerator, drifting, AND braking...impossible with this control scheme.
Further reading: http://www.gamefaqs.com/boards/700050-mario-kart-8/71683644