I've been asked a few times about how I do my final clean-up, so I'm going to give a quick step-by-step since it's kind of impossible to explain with words only.
First off, I want to mention that I do two types of clean-up techniques on this film. Both digital and traditional; digital cleanup is done using the brush tool and Wacom tablet in flash-fairly straight-forward. This is only done on scenes that have very few drawings since I find it very time-consuming. The traditonal method is done using black pens on 23lb Chromacolour animation bond. The idea is to simulate a brush and ink which was standard in the early days of animation before the Xerox machine and the computer.
First I simply take my ruff pencil drawing and place a clean sheet of paper over it. This is totally obvious of course, but I'll mention it anyway for sake of completeness.
The next step depends on the roughness of the drawing-if it is really rough and unresolved I go over the drawing in light blue pencil on the fresh sheet of paper, refining the drawing. I didn't do that step for this particular drawing since it is tight enough for me to see all the shapes clearly.
Next I start inking in the drawing. I always start with the main largest shapes first. Large forms get the thickest lines usually. This helps to give weight and unity to the form-in this case, the head. Also, I try to make sure that the lines are more or less the same weight and define the form (in other words if I was to continue the lines where they are overlapped by other forms they will connect up and create a closed shape.)
Next, I ink in the smaller forms. I am very concious of the angles and curves that exist in the rough pencil drawing and I try to maintain them as I ink in the form. I also try to simulate a brush line by keeping the lines tapered at the ends as well as thicker in the middle apex of the curve. Note how these shapes have generally thinner lines than the main head form.
Now I do the features. Facial features should be the most important thing in a head, so even though they may be small they should be thick enough to stand out-especially the eyes.
Now I get out my finest tipped pen (usually a Pilot Fineliner) and put in the final details. And I'm done!
There are a ton of theories to doing good clean-up and I will certainly not profess to being a master at it. But mainly the ones I keep in mind are:
Maintaining a hierarchy of importance
This is done basically as I stated above, making sure that the large forms have the thicker lines and the important parts of the drawing stand out.
Preserving the essence of the rough
Flip to the rough constantly, it should look as good or better than the pencil rough. Don't tone down any angles or curves!
Keeping the lines neat and clean
Make sure the lines taper at the ends and aren't wiggly and rough looking.
Drawing the lines with flair
Be confident and try to draw curves with your wrist and in an even steady motion.