I mostly use tailor's chalk. My quilting methods have changed through the years, but I always have a use for tailor's chalk. I freehand rather than stencil, but need marks for guidance, so this is what works for me. You can buy inexpensive flat triangles of chalk, or use it in a mechanical pencil. Works great.
I'm probably not explaining this well, but if you google tailors chalk, You will see what I'm talking about.