What I've tried so far:
1. Wash soap (Meguiar's NXT wash)
2. 90% Isopropyl Alcohol w/Microfibre towel
3. Stoner's Invisible Glass w/(new) Microfibre towel
4. Zaino clay bar with NXT wash as lubricant
If the glass is dry, I don't see any marks anymore, so I think I've improved things...