INFO:

In this Photoshop tutorial you'll learn how to turn an image into a reusable brush. Using the contrast in your photo, you can select and invert the image to define a brush. This will only work reliably on high-contrast images, but can also work alongside manual selection methods if you fill the selection areas with black. For example, selecting a subject and filling the subject with black to create an silhouette brush of that subject. In the channels panel I realize there is no varied contrast because of the Desaturate adjustment... so just choose any of them for the Levels adjustment!