Many watercolorists assume that they must wait for the paper to be wet to exactly the right degree before applying secondary strokes that need soft edges. In fact, controlling the edge quality of those strokes has much more to do with how dry the brush is than how wet the paper is. Try this quick and surprising exercise, after you read it all the way through:
Make three 6x6” washes of clear water, one just damp, one quite shiny, and one dripping wet. Now load the brush with plenty of pigment and very little water. The paint should be thicker than what you would use on dry paper. Observe how the brush strokes look on the palette. You should be able to see the tracks of individual bristles before the stroke flows back together. Work quickly, so your washes don’t dry. If you were to make a short stroke in the center of each of your washes, what do you think the results will be? Go ahead and try it.. Were the results what you expected?
In the exercise above, the wetness of the brush was kept constant, while the wetness of the paper was deliberately varied.
Now try an exercise where the paper's wetness stays constant, and the brush gets wetter and wetter:
Make a large, damp, colored wash, about 6" tall and 12" wide. It should be shiny, but not at all puddled. Start with a brushful of a saturated, different color that you know is drier than the paper, and make a stroke off to one side of your large wash.
Now add a little water to the brush, and work it around on the palette. Make a stroke of this wetter color near the first one. Add a little more water, and make a third stroke. Keep adding water, a little at a time, and making a new stroke beside the last one, working your way across the wash, until you lose control of what happens on the paper.
In the first exercise, the look of your secondary strokes is one you will want to use often. In the second exercise, what happens when your brush gets too wet, on the other hand, is something you won't do on purpose very often. Which one would be appropriate for soft-edged shadows?
For the next critique, look for a passage in a scene or an image that could be represented with the kind of strokes you made in the first exercise. Experiment with the wetness of the brush to discover what works to give you the kind of edge you want. Bring in the study and the photo, if you use one.