Nubuck is a delicate material similar to suede that is popular in shoes today. Because your shoes are exposed to many elements as you wear them, nubuck can quickly fade or wear down. When new, nubuck has a strong appearance and a velvety feel, but as it ages, it can lose its color, get soiled and develop flattened areas. To help prevent wear, many owners of nubuck shoes will apply a protective spray to help keep water and stains off the material. Even so, protective sprays can wear off and require you to repair the nubuck.
Brush the nubuck material with a circular motion using the nubuck brush until the bristles of the nap begin to stand up. This will repair any flattened or dull nubuck material.
Clean the nubuck with a leather degreaser to get rid of any stains or marks. You can apply the leather degreaser directly to the nubuck material and rub it out using the nubuck brush.
Apply dabs of water to the nubuck and use the nubuck brush to get rid of any light stains as well as improve the appearance of any areas that may be have flattened out. The water helps the material break up a bit while the brush helps bring the nap back to standing attention.