i've been using a good ole sharp pencil with success to mark fabrics for gee...40+ years...and have never had a problem with it washing out.
i've had plenty of problems with specialty quilting pencils, pens and markers.
write as lightly as you can and still see what you need to see, do your work, when you are done with your project -- wash it...no more pencil marks.
i always test a small piece of the fabric i am going to write on just to make sure, i have never had pencil not wash out. and i've had pencil come off with a good eraser too. but i wash everything i make when it is finished.