In my struggle of learning how to properly draw with pen and ink, I keep looking for the right tools and the right methods, which is kind of hard when you do not have a proper tutor or teacher. Lacking this, the best help is always practice, combining real sketches with other exercises from "Pen and Ink Rendering" by Guptill. These exercises include both training straight and curved lines and also tone building.
What is tone or "value" building? Pens are typically monochromatic and pen drawings as I like to learn them involve only one color. Lacking the option of more colors, the only option is to build gray tones by mixing the dark color of the ink with the white color of the paper until the appropriate balance is reached. This can be done in many different ways, such as drawing parallel lines, or crossing lines at different angles (hatching) or drawing free strokes. And man, this is hard without the right tool!
The picture above shows similar exercises performed with five of the pens that I use most: from left to right, Tachikawa School G, Rotring Art Pen EF, Dilli Flex Nib, Platinum Preppy 0.2 EF, and Guanleming 193 Fude Nib.The spacing between lines is either regular or gradated, and sometimes (bottom lines) I reversed the pen, drawing upside down to try differnt thicknesses. In doing these exercises some things are very obvious:
The good news is that, except for some particular cases, there are only very subtle differences in between many of the thinner nibs (Tachikawa School G, Dilli Flex Nib, Platinum Preppy, Pilot Penmanship, etc), so if you try to follow the same route as I do, you are very well off with any of those inexpensive pens.
The photo above is a test that I conducted some days ago. Today I completed it with the Pilot Penmanship and two dip pens that are considered "standard" in pen and ink rendering, the Gillot 303 and 404. The picture looks uglier because the wetness of the India ink curled the paper I used, which is just copy paper. The purpose of this last test is to become confident that I am using the right tools to achieve the effects that are shown in the pen and ink bible and in other references I am reading, such as Gregg's notes. I must say I am very happy about its outcome: it means one can do nice work with very simple, very inexpensive and available tools.