Use an angled artist’s brush to “cut in” sections next to different-colored panels, piping or welting, stitching, seams and embroidery.
You can also cut a sponge on the diagonal to make a more precise wedge. Masking tape can be helpful, but Rub ‘n Restore® colors are very runny and may bleed beneath it.
Use a sponge for broader areas that don’t require precision.