Digital pencil doesn't seem to act like real pencil
I've been watching this tutorial "http://www.klinecreative.com/art/artlesson1.htm" about actual pencil and paper art, and the first thing the guy demonstrates is that you can draw really light lines with a pencil and the more you go over them the darker they get.
I've tried doing this with several digital programs using various pencils and it doesn't work. No matter how many times I go over the same line it doesn't get any darker.
The closest I've gotten, using ArtFlow, is to set the color to just below white (245,245,245) and then use the 'multiply' blend mode. Is there some reason that digital pencils act differently from the real thing by default? Are there other settings/techniques I should look into? Or maybe these tutorials are all full of s**t?