You could try a white pencil, but you could also draw the stencil onto regular paper, enough times to cover whatever area you intend to FMQ. If you will be using an allowed pattern on the top, fill the entire page if you like. Get a stack of very thin paper. Go to the sewing machine and, using an unthreaded large topstitch needle, with a small stitch, sew through all the layers. The holes will function as a pattern for you.