I have the Sewline mechanical pencil set but found that I had to press hard to leave a mark and felt like I was stretching my fabric (drawing diagonal line on square to make HST felt like it was distorting the fabric too much).
I've been using a washable marker pen for now but need to figure something else out for marking lines that are on the seam line (like when you need to mark a square to make a snowball block) and could potentially be visable in the finished quilt block.