I tied some flies with the new uv2 materials last winter, and have lost track of them. Some I can find by shining my uv light on them, but not all the materials show up. Is there a thread I can use for the heads on these flies so I can identify them? I know there is a fluorescent thread, but some I don't want to be bright. I use different colors for the flies depending on body color, so what other options do I have?