I use a mechanical pencil, very fine lines and always wash afterwards. Never had a problem with the lines staying on the fabric.

the reality of removing marks is.........what might work for you doesn't necessarily work for me. Many factors such as: washed or unwashed fabric, type pencil, pressure put on marker. Regular pencil has wax in the graphite that makes it difficult to remove. Some have more than others. size of marked line - sharp vs wide line.....
So the botton line is to always test before marking to make sure.

I have started using pencil and eraser. It is better to use cheap pencils and I forget what size lead they are. I use the cheap retractable lead pencils that you can get at the dollar store, etc. Very light pressure but I have erased darker lines too with a little more effort. I have used the blue disappearing markers but had trouble with the blue coming back after being washed.

Baby wipes work wonderful for removing pencil and marking pencil lines

i left some pencil markings on a quilt top for about two yrs and soaked it in Oxy clean and also rubbed the lines while wet. they came out. good luck.

Baby wipes fix everything in this house. Works great as a makeup remover as well!

I know it works on ink. Haven't tried pencil.

WOW! That's good to hear!

I use a fabric eraser, looks just like an eraser but is made to remove pencil markings on fabrics. Got it at my LQS.

I've never had good luck with a pencil. All I use are the washable fine tip blue pens. Love, love, love them. I've never had any trouble getting the markings off my designs.