Are you hand quilting or machine? I have heard good reports on the water soluable quilt pens that you just draw your design on the fabric with. I think they would work with the quilt already sandwiched. I think a pounce with chalk and stencil would also work. (With any marking method always make a test sample, quilt it and try to remove marks.) I have a Fons & Porter fine chalk pencil in white that I like on dark fabric. It is supposed to rub off but I did have to wash the quilt to remove the marks. If you are machine quilting, the golden thread papers are good or stitching through a design marked on Glad Press & Peal.