Blending of colors or values is most easily accomplished by starting with light applications of two or more colors. Drawing many light applications in possibly many directions will cause the colors and values to appear to move and transition smoothly from one or more colors or values to other values and colors. In watercolor blending is achieved with the successive application of many layers of thinly colored water that you allow to dry between applications. In watercolor and other paint you can achieve blending by changing the color from one color to another color while the paint is wet. This takes practice because choosing the colors, "loading" the brush and using pressure that will be right for your paint, surface and desired effects requires lots of experimentation.