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Since the watch has a sapphire display, I just don't care. So I use my shirt 😛

About once every few weeks, I've gotten in the habit of cleaning it thoroughly and I just use the microfiber cloth that came with my Macbook Pro.
 
I really like the "e-Shammy" microfiber cleaning cloth. Works really well for all my devices. I believe I got it on Amazon.
 
I'm a photographer so I am a bit picky about my microfiber. I have a bunch of Adorama microfiber cloths in small and medium sizes: http://www.adorama.com/CPCMSK1.html

Not that there is anything that special about these...there are plenty of good microfibers out there, but there are even more bad microfiber cloths. The ones with looser weave or that are thicker are pretty much useless (they feel more like synthetic chamois than microfiber). Thin and fine weave do a much better job.

I will also admit to using a tshirt to wipe off my watch or phone from time to time... but I stick to microfiber for my expensive lenses.

Sean
 
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