To answer this question, it seems like a good idea to practice seeing the middle values as an isolated layer, apart from the influence of the lights and the darks. Just as we sometimes paint the darks alone, to see how much of the story they tell, the same approach may reveal the role the mid-tones play in a given image.
Here are a couple of images that seem to rely on the middle values for essential information. Try quick rendering of only the mid-value shapes. Keep it simple. Lift your brush from the page as little as possible.
If the layer goes on the paper good and wet, you will have time to vary the color of the wash without creating overlap lines. The fewer individual shapes you use, the easier it should be to get an instant "read" of the content.