One of the most common ways watercolor paintings go wrong is by having too many hard edges. The jittery look of insistent shapes everywhere on the page can be difficult to avoid unless you have some practice determining which edges really need to be distinct. What follows is an exercise that may provide a way to tell what kind of edge is appropriate. It's based on the assumption that the best way to know if something belongs in the picture is to leave it out. In this case, the whole idea is to make a version of the painting that has no hard edges at all.
Like so many things about watercolor, this is easier said than done. The paper often dries before you've had a chance to lay in all the washes and strokes you want. It helps to be watching for the first sign of a hard edge, and to take it as a giant STOP sign. You can then dry the painting thoroughly, re-wet it, and resume making soft-edged marks that look like they were made when the initial wash was still wet. Remember that re-wetting should be done as efficiently as possible to avoid disturbing the previous layers. Apply a coat of clear water without going back and forth too much. And, did I mention that the paper needs to be DRY before you can re-wet it?
Most of the wetness control issues that arise when working wet on wet are caused by not making the first wash wet enough, and then having too much water on the brush when the secondary colors go in. Practice and experiment! Technical skills are easier to strengthen when you're not in the middle of what you hope will be a proper painting.
In the first photo, below, imagine you're about to paint the nearer hill. Since all the colors involve yellow, you could start by laying down a yellow wash. Make it nice and wet, that is, shiny, but not dripping wet. No pools of water. That wetness plus any that remains on the brush are all the water you'll need for what comes next. So, without washing your brush, add some green to it, and make the pattern of middle -value strokes that represent the shadows. Then add some darker pigment (not more water!), and make the array of the darkest spots. Since the sequence goes from yellow to green to darker green, there's no reason to wash your brush. Each successive layer is darker and thicker than the previous one.
The soft-edged study can be very simple and still give you the information you need. Stand back and ask yourself where you wish there was a hard edge. Imagine that you only get to make one. That will help you look for the most important place to draw more attention. Proceed with one placement at a time, standing back after each one to see if you've added enough. Remember, the idea is to develop a sense of how to stop without going too far. Err on the side of too few hard edges, rather than too many.
I recommend reading this all again before you start. Thank you.
Here are a few images from the Methow Valley, in eastern Washington.