I have not brushed them vigorously. Are they a candidate for brushing with a horsehair brush? I have used a suede brush on discreet parts of the shoe to test how that would work. This leather does not have nap like a suede. It is more of a smooth leather; think 24 grit versus 220 grit. In my opinion, vigorously brushing would pull oils out of the leather and cause the darkening. Therefore, I have avoided it. The darkening I can understand, the creasing is what upsets me.