Also, they work great only when they're new.
My brother in law made a lighted glass board during covid so he could write in mid-air while facing the camera at the same time. He used light-colored whiteboard pens and a dark background.
All that's missing was to write in reverse because the camera was on the other side!
"Good paint pens" are so expensive... Also they go through standard printing paper so they need expensive special paper...
That being said, i don't draw/paint, so i don't understand the appeal of these special pens.