Does this help?
Forearm Rockers
Type of movement: Midrange
Auxiliary muscles: traps, shoulders
Think of these like a way to combine wrist curls and reverse wrist curls. Take a moderately heavy dumbbell in each hand and stand up, then curl the wrists toward the body, then away, rocking the dumbbells back and forth, hence the title. These will burn like crazy, but don't let the fact that you'll look goofy grunting while doing them stop you, they're a fabulous forearm developer.