Anything you can do in traditional cartooning can also be done on a computer. Here I give you an example of pattern transfer sheets. Pattern transfer sheets are sheets with patterns on them that the cartoonist can use to quickly draw patterns, such as dots or fabric. You can do this on a computer by pasting your cartoon over your pattern sheet with the area it is to fill painted with the mask color.
The first thing you need to do is draw the pattern sheet. I have include several examples in the download. Your pattern sheet can be anything you need, not nessicarily just a "pattern". I usually make the image I use for the pattern sheet 320x240. You can paste several copies together if you need it larger. When finished make sure that you save it in a place that will allow you reuse it easily.
The next thing you need is your cartoon. Once you have both you can open your cartoon in QuincyPaint. Now goto the "Layers" menu and switch to another empty layer. On the layer use the"layers-import BMP" menu to import your pattern bitmap. If the image is a different diminsion QuincyPaint will ask if you want resize the image. You probably want to select "no". Now you may want to copy your pattern sheet and tile a few of them together to insure it will cover the area it is to fill.
In the image above I want the pants on this character to be plaid. So I make sure the right mouse color is magenta. And I fill the pants that color. Now I just select and copy the character. Then I switch to the layer with my pattern sheet and paste the chacter over the pattern sheet using the right mouse button.
Here is the final result. Remember to keep your pattern sheet for reuse. Also, a pattern sheet can be full color.
TIP: More advanced GRFX programs can just fill in patterns(I like "the GIMP" it's free and as good as $500 programs.). But you may not always get exactly want you want.