The tools I used for etching the lines. The carving pen looks like a mechanical pencil, I use it to define the lines and sometimes for sanding hard to reach tiny areas. If you are interested to get one, you can find it at Tokyu Hands when you are in Japan or check out your local Tokyu Hands store.
It is always fun to do the sketches but most time the actual finished product will look slightly different. I do struggle with the decisions every time but eventually I will settle with "simple is better".