Have you ever struggled with a passage even though you know the colors and tones are right? One corrective, especially when the tones are extremely close, is to ensure that closer forms are painted over those farther back. I don’t know how many times I’ve seen works spoiled when things farther away are painted over things that are closer.
A simple example is, say, an apple consisting of only two tones. If you apply the lighter tone over the darker, the eye will more readily accept the verisimilitude of the form than when the revers is done. As we know, when the eye (mind) accepts the truth of a form, not only will it overlook clumsy passages, it will assist in correcting them itself–magic.