I have this stuff called Perfection Master Crayons. It is fantastic for marking dark fabrics and the beauty of it is that it doesn't rub off like chalk and to get rid of the markings, you just need to put some steam from your iron on it! I got a box of these in a grab box I bought at a yard sale. I'm attaching a web site where you can get them but I have never bought from these sellers and I'm sure you can find it cheaper (maybe???)
http://www.universalsewing.com/tek9....riteria=209.16