I have been experimenting with line and wash–but not all my pens have waterproof ink. In fact, many of my favorite drawing pens use water-based inks. Adding a watercolor wash would smear everything.
So I picked up a handful of Copic markers (brush on one end, chisel tip on the other) which are alcohol-based. I did a simple drawing of a tree and roofline with water-based ink using my favorite pen, and then applied color with the markers. (I have a more complex sketch in progress with this same pen…you can see where this is going.) It’s just a little 3″ x 3″ sketch to see if alcohol markers will co-exist safely with water based inks.
I’m very happy with these markers. They come in a zillion colors, so I think will be able to color all kinds of ink drawings with them nicely.