This is a tough one to work with for sure. I teach Pilates and always tell my participants that have pain from piriformis syndrome to avoid any movement that causes pain. (No lateral flexion movements, circumduction or anything that engages the medius & minimus). They can be pretty limited with range of motion and regular movement when suffering from this and I recommend they ice and rest. I focus on piriformis stretches for them whenever possible.
Good luck with that one!