I'm a traditional media artist (markers), and my most time-inefficient step is definitely re-inking. What do I mean by that?
I mean that my order of operations is as follows:
Rough pencils (to place major elements in the panel and roughly figure out proportions, gesture, and the like)
Final pencils (to actually draw all the details)
Inking (going over my pencil lines with ink)
Erasing (to remove the pencil lines)
Coloring (Duh, to add color)
RE-inking (to darken my ink lines that got faded during the erasing/coloring process, and to clean up any messy edges)
I COULD consider my work done after the coloring stage, but re-inking makes it look so much cleaner and more finished. It's the time when I fix small errors, or tweak line weights, or sometimes add other little textural details. And it takes about as long as inking the first time around did, so it's definitely time inefficient. But I do it because unfortunately, it does make a difference. (See below, the 'before' on the left, and the 'after' on the right.)
