I use a trick in my art that I don’t see people talk about often: erasable pens!
Most people seem to use pencil to make their guide lines, and then go over what they want to keep in ink or paint. I’m a watercolor painter, though, and if you go over pencil with watercolor paint, it seals it in.
If your pencil drawing is good, that works out fine, but my drawings are not. I don’t draw freehand, so I’m usually tracing a reference image. In addition to my lines, I mark out where my shading and highlights are going to be, which is all very helpful when painting, but I don't intend on keeping it in the final image.
They're "erasable" pens. They've got a rubbery bit on the end of them, you rub that on your pen lines, and they erase. But how it actually works is using the heat from the friction to somehow turn the ink invisible... which means you can skip rubbing the eraser on it, and just use heat directly, such as from a heat gun that a lot of crafters have (or just a hair dryer will do the trick too.)
As you can see in the video, I drew out some shapes, and then painted them with watercolor paint, using the lines to put my paint where I wanted it. Then I point the heat gun at my paper, and you can watch the lines vanish, leaving just the paint behind.
What this looks like in my process is this. As you can see, I've outlined all the lines of my subject's face, but I've also got areas that I filled in to indicate where I would need to shade more heavily, like along her jaw, on her neck, and in the inner corner of her eye; I also created directional lines for a crisscrossing pattern on her bonnet.
In the final version, once I was satisfied with all my painting, and I had gone over the lines I specifically wanted to keep in a permanent pen, I pointed the heat gun at it and watched the lines disappear. Now only the shade remains, and the pattern on the bonnet isn't as harsh; I've also used the pen to let me paint a plaid pattern on her cape.
If you look closely, you will see the shadow of lines within the shaded parts. Sometimes, the indentation of the pen tip on the paper will cause a slight relief drawing situation even after the ink disappears. You just have to remember to draw lightly.
I found the pens at Target for not too much money in the 0.5 size, and I just got some 0.38 finer line pens since I need to do more detailed work on my current piece.
Anyway these are SO easy to use, and I really enjoy being able to do art at the skill level I'm at, and doing it like this allows me to. Have fun with art!