I used a Japanese dip pen for crosshatching. It's just a basic technique for most cartoonists and illustrators. You can take a look at my simple tutorial on how to create gradient crosshatch. [link]
Thank you for the tutorial, Rina! I thought it was something like stamping; omg now I see how much work you put into it it seems to be not so easy but I must try, thank you again you have shown me something new