Problem marking nylon, Help!

Try a more or less worn thin old bar of soap. Or if necessary carve a sharp edge on it. The soap will rub off or wipe off with something damp. This works great.

there are many specialty marking tools you can use for this purpose, chalk pencils or markers that are made to wash out… you could find them at any craft or quilting store.
of course, soap would work as well, and is basically free.

I find prismacolor pencils work really well. If you've got a friend that draws or who's an art teacher. They mark well and then rub off easy. Most art stores also sell them loose.

JFF