How to keep scratch art paper clean and free of pencil and eraser marks? I was introduced to scratch-art in high school and have loved it ever since. The problem I repeatedly encounter is in keeping the surface of the paper unmarked where I want it to remain black. I have tried a number of solutions as far as a storage is concerned, like keeping it between two pieces of paper and even buying a folder carrier for my projects to keep them protected. I don't wear jewellery when I work and that helps a lot.

I find though, that my faint pencil sketch I do before starting often shows up and is difficult to erase. the pencil is very shiny and reflects a lot more light than the paper does. The eraser makes more ugly marks than the pencil does. Further, I haven't figured out what to do if I do make a mistake. 

Does anyone have tips for preventing ugly marks on scratchboard paper or fixing them once they've occurred?

Is there a suggested medium to sketch with on this sort of paper to lay out the outline of a design?

Here's an example of one of my projects:
I have not done any sort of serious scratch-board art, but here are some suggestions, to answer your two part question:

Use black colored pencil instead of regular pencil.— it isn't as reflective as regular pencil, so you will just barely be able to see it while you're working.

Paint over the nicks/stray pencil marks— If you paint over the scratches and stray pencil marks with ink, it will probably cover it up and not show.  You should try this on a scrap piece of paper first, to be sure.