Drawing on Multiple Layers of Vellum

I've been intrigued by the thought of experimenting with colored pencil on multiple sheets of drawing vellum (also called drafting film in some cases) in which one layer would show through another to give my composition a 3D type quality. I purchased several 18x24" sheets of Duralar matte vellum and chose my photos of carousel horses for my composition. My intention was to use three sheets of the film; one for the foreground, midground and background of my drawing. I started this piece in January, using Prismacolor pencils and working first on my three foreground horses which will be the focal point. Next I moved on to the second sheet of vellum and began working on the next grouping of carousel horses as they recede for the midground (top photo) and the objective is to have these horses fade a bit into the background. I had planned the third sheet of vellum would be used for the shadows and part of the carousel center.

However, as I began to work on the multiple layers, I quickly found the vellum isn't quite translucent enough to achieve I color I need to show through on multiple layers. The vellum is smooth and takes the pencil beautifully, colors are rich and intense on the surface. What I like about the translucency of the vellum is that I am able to work with the colored pencil on both sides. The smooth surface only allows minimal layers of pencil and if I've saturated the front, I turn the sheet over and continue on the opposite side to achieve additional color and value. It is also easy to erase mistakes with a drafting eraser and I've also heard rubbing alcohol will remove smudges and fingerprints but haven't tried it just yet.

What I have learned so far ... I'm going to have to adjust my layering process. I may only use two sheets of vellum instead of three. I may add more of my composition to the top layer and let it fade into the next layer. It's trial and error as I work but learning and enjoying the process.