Cleaning Nubuck can be challenging. It seems like there isn't a straight forward solution for all types of nubuck. If you're working with light colored nubuck as shown above, using a product like Lincoln EZ Cleaner or Diswashing soap seems to work fine. However, if you're working with darker nubuck, you're going to want to use the brush from the Suede and Nubuck Kit from Footlocker.
The video below will explain most of the things you need to know: