You can work Your shoulders without weights. We know we can do isometrics, self resistance, visualized resistance and calisthenics. Here's something from Jeff, something I would say are tension calisthenics.
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Health, Fitness, Non-Apparatus Exercise, Unarmed Self-Defense, Firearms Self Defense
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There are some interesting exercises in the lying positions while the stomach is facing down:
9 Active Tension Exercises for Shoulder Mobility
https://www.vahvafitness.com/active-tension-shoulders/