The process is quite simple.
I often work with water soluble pencil - both watercolor and graphite. I relish the control of drawing and shading with them at first, but I also enjoy the painterly quality when water is brushed over the pencil. I frequently use multiple layers of water soluble pencil to begin pieces allowing each layer to dry before adding a new one. I work quickly and spontaneously with the water soluble material, but at a certain point, I feel the need for more control, sharper edges, and more defined values. I then switch to regular graphite or colored pencils that allow me the precision I desire. I darken areas making them recess into the space. I straighten edges and redefine areas, shapes, and lines that have been lost. It is a slower and more tedious process, but I love the outcome.
I used water soluble graphite pencil in the piece above to lay in the foundation of the piece. Notice that many of the edges are uneven, that there isn't much contrast, and that the swirly lines are barely there. I started the piece below at the very same time as the piece above using a similar technique. I built layers of straight lines, rectangles, and organic lines with the water soluble graphite pencil. Once I felt that I reached the limits of what the water soluble graphite would allow, I reworked the piece with a variety of regular graphite pencils to define the spaces, lines, and values. It is nearly complete in the photo below.
Below is a photo as I worked on the main focal point.