[@Unfortunately]

I used to use ballpen as well, but recently I've been trying my hand at a Sign Pen for tracing my art these days, simply because it shows up better and cleaner if you get used to it. After that, I take a picture of the traditional art before using the "Threshold" tool to whiten it up before selecting all White colors simultaneously. I then cut it out. I THINK I used the Selective Color tool for this, but I forgot since it's been a long time since I actually tried this method out.

Threshold tool is not good for ball pen lines, but for thick lines like Sign Pen lines, it'll catch and show up pretty smoothly. I strongly do not recommend path stroking because that's mostly useful for Vector Drawing or tracing over lo-res images to make them higher-res rather than for regular drawing. Also, unless you know gradients, it will be supremely hard to make the art actually look fancy.