[Syzygies]

Professional Korean 70/30 Super Plush 500gsm Microfiber Detailing Towels (16x16, Blue)

https://www.amazon.com/gp/product/B00GXRG64I/

In Germany they outfit classrooms with sinks and squeegees.

Over decades I've tried absolutely everything. I see colleagues in earlier stages of evolution on this (e.g. carrying a squeegee and a bucket), but mathematicians are unbelievably stubborn (think zebra) so one learns not to say anything. This is like debating programming languages: If all parties haven't written significant projects in all languages under debate, just learn to walk away.

Wet or dry, nothing beats a Korean microfiber auto detailing cloth. One or two passes damp (not wet enough to drip while walking) will clean a board better than the overnight cleaning staff. Dry will erase better than any eraser.