I grid my works with different colored sewing thread, for example red on white fabric (if the pattern doesn't have too much red, and so the gridding will be noticeable) or yellow on blue or black fabric.
I am using the water eraser pen from Jpan and it disappear in 2 days. It is more like air eraser... I have also tried the pen made in China, which look like normal pen and they are always there. Soaking in tape water 10min can erase all the marks
hello. yes i do mark or grid my fabric for easy counting. i use DMC Water erasable pen that can be bought in craft store. sometimes if I dont have that pen, I use Yellow Crystal waterbase pen or yellow Crayola Ultra Washable marker