I'VE TRIED SEVERAL DIFFERENT TYPES OF MARKERS AND HAVE FOUND THESE TO BE THE BEST OF THEM ALL; "STABILO" BRAND CHINA MARKING PENCIL "AQUARELLABLE". I USE BLACK (#8008) AND WHITE (#8052), THO THERE ARE OTHER COLORS. THEY MARK EASILY, WASH OUT COMPLETELY AND ARE RELATIVELY INEXPENSIVE. I ORDER MINE BY THE DOZEN AT A LOCAL ART SUPPLY STORE. HOPE THIS HELPS!