I too have yet to find the "right" marking pencil. I was going to get some frixion pens to try. I went on line to see where would be the closest place to buy them and stumbled on this lady's blog. She has done some experimenting with the frixion pens and has posted pictures of the results. It was very helpful. After seeing her results, I don't think I will be buying these. Here is the link if anyone is interested.
http://mythreesonsknit.blogspot.com/...s-warning.html