This tutorial is about drawing manga in a quick way using mouse. But tablet users can also apply this style. In this tutorial, you will be taught the magic of fill+line tools.
First off, choose a background color because it makes all the surface an even-toned color.
Then using fill tool, make a rough shape of what you want to draw. I usually draw the skin first. If you feel that what you've done doesn't resemble what you wanted to draw, then use undo (del key).
Using guide tool, create a cross guide for the face (optional). Then add a rough version of some details. (In this case, hair and eyes.)
Now, using line tool, smooth out some rough surfaces, and add additional details.
To add shading, also use fill tool with low transparency. I usually choose really dark shades of a certain color and set to 10-20% transparency for shading.
Now add additional fine shading and light effects (also using fill tool). And there you have it. A quick manga drawing using mouse.
Note: for highlight of the eyes I used white with about 40-50% transparency and drew it several times until the overlapping transparencies create an almost pure white hue. I also applied the same technique for the eye color, but I used different tones of blue.