A chopstick, small paintbrush, or pencil will work fine. Go with something you’re comfortable with modifying. Don’t select, for example, your favorite pen. For the adhesive, you can use poster putty, double-sided tape, a bit of glue from a glue stick, or even chewing gum.
With practice, you might be able to skip the adhesive altogether, and use the stick to keep the pick anchored to the base of the guitar, against the inside label, as you flip the instrument over and let gravity do the rest. [2] X Research source
