Rtistx board. I've finished the foreground stones, which took me a few weeks because I found I could only concentrate for a few hours at a time because of all the elements and detail. I've been using Polychromos, Prismacolor and Lyra Rembrandt pencils for the rocks. Let me tell you why and what my technique is. The Rtistx board is a sanded surface and I find the Polychromos work best for the first layer of color. After I apply the color, I burnish it with a bristle brush to even out the tone. Polychromos aren't as waxy as other brands so they tend to rub into the paper almost as a pastel stick would. Next I apply layers of Prismacolor and Lyra Rembrandt. The Lyras have an oil base so they don't crumble as much as the Prismacolors. However, I also have to choose my pencils according to the colors I need for the rocks. Because I'm working from the bottom upwards and leaning on my drawing, I will put a piece of clean paper under my arm so I won't smudge the drawing I've already done. I also spray with workable fixative between layers of colored pencil to keep the pencil from lifting or smudging on the board.
After I've applied the color, there are still some areas I want to look smooth but sometimes doesn't because of the sanded board surface. If the rocks look too textured, I hit the surface with a soft brush and some odorless mineral spirits which dissolves the pencil pigment so it moves like paint. I brush it lightly so I get the effect of watercolor paint. One of the brushes I like to use is a Mongolian Sable 1/4" flat from Dynasty Brush Company.
My next step is to continue working towards the top of the drawing where the waves and white foam are encroaching on the stones. The easy part about the top is that much of the board will be left white to show the lightness of the foam.