I started digital inking in Clip Studio. The brush/nib(s) I've been using for all my line art is Frenden's Manga Studio 4 Flexible Nib- it gives me all the lines I want to make at the line weight I like. It also allows me better control, as some brushes have a bit of play to them & I struggle to keep my strokes under control. The second brush I use to get finer lines than the first is Frenden's MS Organic Brush- nice thin lines, but still allows me a great degree of control over how I want my lines to look. I use the lasso & fill tools to spot blacks.
The Frenden brushes do not come with Clip Studio, but you can get them at Frenden's website for $6 bucks-they come in a set with about 20 or more inking brushes/nibs/pens.