Here is a nice little video on how do use gel pens with your coloring books, and how to get different effects using them.
The artist demoed four different brands of gel pens, Tekwriter, Super Gel, Sakura Moonlight, and Pilot. The first three can usually be found in artist supply stores or online. The third type is often used on black paper. Isn’t that cool? The last type is just a simple, cheap gel pen commonly found in office supplies stores. She clearly had a preference for the Tekwriter, but did convey that all can be used.
Part of the demo showed solid applications of the gel pens by themselves, but most of the demonstration was devoted to gel pen use with colored pencils and techniques for blending colors using either a dry brush or damp brush.
One interesting thing was that applying a gel pen over colored pencils and using a slightly damp brush or even a dry brush for blending allowed color to be pushed into the white spaces left in applying pencil color without bleeding through the paper. Wax in the pencil made a protective barrier for the sometimes thin coloring book paper.
A really cool part of the demonstration was the use of gel pens with a damp brush to fill in some of the really tiny places in an image that you usually can’t get to. He created a really nice color wash that got into those small spaces.
The last part of the demo was a comparison between the different brands of gel pens. I have linked to the most interesting ones.
Some of these techniques I am definitely going to experiment with.