Drawing by hand is a great skill-builder and important for developing your observational talents. Drawing is, as they say, not so much about hand-eye coordination (or even imagination) but about seeing. Sometimes, however, it’s fun to just throw down some lines.
One of the tools I enjoy using from time to time is a cheap opaque enlarger.

It’s basically just a bulb that blasts an image, that is then reflected onto a vertical surface. You need about 10 feet of distance, depending on the size you want to enlarge, and a dark room. (The larger you enlarge, the darker your room needs to be, and the more space you need.)
You can enlarge anything but it should be high-contrast and no bigger than about 6 inches tall.
I generally blast the image and pencil in the main contours and key tonal shifts. Then I draw over the whole thing without the projection, (in Sharpie marker, in this case), and make selective alterations to improve the image.

John Zorn, American acid-jazz saxophonist. Sharpie marker, butcher paper, about 6’ tall or so.
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