For dark brown smooth leather, a colored shoe polish or care cream in a matching shade of brown is best, as it nourishes the leather and intensely refreshes the color. Alternatively, a combination product like Golden Bull Readymix is a good option, as it cleans, conditions, and protects the color without leaving stains. It's important to thoroughly clean the leather with a dry cloth before applying the product and then apply it evenly with a soft cloth or sponge.