I had started these by doing embroidery, and quickly realized it wasn't going to work out. 1: it was going to take WAY too long and 2. the back of the embroidery would easily show, and it did not look pretty. I than remembered the gel pens (I used a Sakura Gelly Roll pen) are permanent and also easy to work with. You can also achieve more detail, especially when working small.
I had to draw somewhat slowly to make sure the line of ink wasn't breaking up, but it was much quicker than the stitching. After you draw your artwork, heat set the ink with an iron. After that it can be washed and dried and the ink will stay in place.
