Certain sketchbooks are better suited to mixed media than others, and while I've never done formal tests or reviews on sketchbooks, I have my preferences. I prefer Blick Sketchbooks to Strathmore (heavier paper, better tooth), and I use Strathmore Multimedia sketchbooks for marker tests. I'm not really a big fan of Moleskin sketchbooks, but I've seen a lot of artists use them for exciting multimedia sketches. In the future, I'd love to test out different sketchbooks, but that requires more dedication to a paper I might end up hating than I'm willing to commit right now.
For my more recent adventure in multimedia sketching, I kept to my favored Blick Sketchbook, but pulled out my Cool Gray Copic Sketches. I've noodled with fude pens and Copics before, usually on cardstock. At that time, and for this test, I've let the Kuretake Fudegokochi ink dry overnight before erasing the nonphoto blue lead, to prevent smearing and to ensure that the ink is able to dry fully before the eraser picks up some of the carbon. Not waiting long enough before erasing can lead to your ink picking up, leaving your lineart looking gray rather than black. You should at least wait an hour before erasing, whenever possible.
I do know that Copic Multiliners ARE Copic marker safe, and that Sakura Microns are supposed to be alcohol based marker safe as well, and while those have their place, I really prefer inking with fude pens.
The Original Lineart
Erasing Those Bluelines
Preparing to Tone
At the time, I was displeased because there was some smearing with the Copic Sketch smearing the fude ink. I think this happened because my Copic was running dry- they have a tendency to really muddy a piece if they're too dry because the brushes will pull rather than glide. I'll revisit this technique after I've had a chance to test and refill my marker collection.
And I just darkened her eyes and hair with a Pentel Pocket Brush once I'd finished toning.
Using Copic markers to tone sketches is a fun way to add a little color to your sketchbook, or to more fully render an idea. As long as your ink is waterbased, it SHOULD be Copic-safe if you've let it dry fully, but you should always test ahead of time to make sure.