The trick to thin arms is to smear Fu Jiao Ya, and you can also do arm slimming exercises when you are free:

Action 1: straighten your hands forward, stand with your feet shoulder-width, draw circles with your hands, draw circles outward for 20 times, and then draw circles inward for 20 times. Don't draw too big a circle, use the strength of your arm, not your palm.

Action 2: Stand up straight, spread your feet about shoulder width, spread your arms to both sides, straighten your palms outward, and slowly circle forward for 30 times.