If you use fountain pens for journaling, and want to add texture to your doodles, consider adding a waterbrush and water-soluble graphite to your case.
My old comic strips were unrelieved black and white, with an occasional foray into gray. Even now, I find relief in grayed pink, grayed turquoise, grayed color – pure shades can still scare me.
This is a thick Lyra pencil. Cretacolor also makes water-soluble graphite pencils, as does Derwent.
After you doodle, go over the lines with a waterbrush and use the wash to fill in the spaces you want. This brush is already carrying a little graphite, for a grayer result.
So what you get is almost like a duotone print. It’s fast, and you can do it while you’re sketching on the go.
Here’s what the theoretical journal entry looks like.
Of course this technique works better with non-waterproof inks.