Steel wool won't harm glass, UNLESS abrasive particles are already present on the glass. Unfortunately, aluminum oxide is common in "dirt." It won't take much aluminum oxide to scratch glass. So, before polishing glass, remove the bird poop and dirt with lots of water, detergent and a soft cloth. Then, polish with a commercial compound intended for that purpose, like:
https://www.amazon.com/Cerium-Oxide-Glass-Polishing-Compound/dp/B009XUAA4Y
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