CARs (Controlled Articular Rotations) Time under tension is key, don't rush through. Generate and maintain as much tension as you can throughout the whole range of motion.
Assume a prone position, legs together, forehead resting on the floor. Start with your arms relaxed, hands are resting on the lower back, palms facing upward.
Keeping the upward tension, extend your elbows until your arms are straight, and begin rotating them out to your sides in a circular motion. As your run out of range (arms should now be about 90 degrees from the body) Rotate your palms facing down, maintaining tension. Continue the circular motion, until your arms for a Y shape overhead, then reverse motion.
Keep your arms as far from the ground as you can.