I have found the cermanic mechanical pencil to work great on black. It will come off with eraer. The pencil is made by: Sewline, Fons & Porter, Bohin and Collins.
I use the black plastic lint brush for erasing. It acts like both eraser and brush. i just gently brush until the line are off. Also works with chalk pencils (For chalk I use the Multi-Pastel chalk pencils) They are made by General Pencil Co and available in some LQS and art supply stores (perhaps Michaels has them). I use only the white and light gray multi pastel chalk as it is washable and has no color pigment in it. Some quilters have successfully used colored chalk pencils but I have never had any success with them.

I don't understand from reading your post if you are marking on black wool or black cotton fabric. It will make a difference what you use for marking.

Thank you for all of your suggestions. All great ideas. I will be marking on black cotton, but appliqueing with wool. The pattern also has a lot of embroidery that would be on just the black cotton, & would require marking directly on the black cotton. I think I'll try the tulle suggestion. I also love the Sewline pencils as they make a very fine mark.