Frixion gel pens for light fabrics-- the marks stay until you iron them away. And they REALLY work! Come in a variety of colors so there's plenty to choose from. For dark color fabrics I go back to my SewLine markers. The lines hold pretty well. One of my friends took a clover chaco marker removed their chalk powder and put in the pounce iron off powder. She says it marks fine and likes that it irons away when she's done. Since I still have plenty of refills for my Sewline, I haven't tried that yet.