How do you make charcoal powder with charcoal pencils?

You can make charcoal powder from charcoal pencils by rubbing the pencil against sandpaper.

Here's a more detailed explanation of the process, based on the video reference:

1. Gather your materials: You'll need charcoal pencils (either standard or compressed charcoal sticks can work), sandpaper (a medium grit is usually best), and a container to collect the powder.
2. Rub the charcoal pencil on the sandpaper: Hold the charcoal pencil firmly and rub it back and forth against the sandpaper. Apply gentle pressure.
3. Collect the charcoal powder: As you rub, the charcoal will be ground into a fine powder. Ensure you are doing this over your collection container (a jar, dish, or even a piece of paper folded to form a trough) to avoid making a mess.
4. Repeat until you have enough powder: Continue rubbing the pencil until you have accumulated the desired amount of charcoal powder.
5. Use the charcoal powder: You can now use the charcoal powder for various drawing techniques, such as applying it with a brush or blending it with your fingers.