In watercolor paintings it is the masterful use of washes that creates depth, spontaneity and atmosphere. Joe Garcia provides clear, simple step-by-step instructions that teach the four basic washes: flat, gradated, wet-into-wet and streaked. Painters will find plenty of guidelines and 33 demonstrations that combine these techniques to create light and shadow effects, as well as a variety of textures for popular subjects, including rocks, clouds and sand. They'll also learn how to develop unique textures and special effects using salt, a palette knife, masking fluid, sponges, dry brushes, spattering and lifting techniques.
I got this from the library after reading a recommendation for it. It's okay but for me, YouTube tutorials from Steve Mitchell (The Mind of Watercolor) have been more helpful.
This approach in this book is nice because it focuses on just four basic washes, and then shows how much mileage you can get out of just those techniques. Admittedly, a lot of the extra example paintings seem to go considerably beyond them, but at least you can see how they're based on these techniques. And the more basic exercises are generally pretty do-able (at least the ones I've done so far). I also like how the painting captions always specify the size, and a lot of them are relatively small, especially for the exercises. Once I noticed that, it got me doing lots more, smaller, practice paintings, which is much less intimidating, and makes it easier to get more practice in.