I never add turpentine, or oil, to my hand-colored prints. Anything that's in the air (pollen/dust/etc.) will stick to it.
When using pencils, I blend them in with typewriter erasers. The eraser smooths out the texture, while slightly intensifying the color.

Randy- You might try oil paint, rather than the dyes. Much easier to work with. I have a bunch of examples in the Gallery, and on my website, if you'd like to see the results I get without additives.