I have read this as well however the dispersion is not nearly what it would be when sprayed. Most if not all hardeners are iso based. I would love to know if there exists a 2k system for AU that doesn't use them, but even water based systems rely on isocyanate hardeners. Non catalyzed systems exists but the finish is not nearly as durable. 1k clears basically suck. For sanding I would think wet sand with gloves, mask and a suit ideally outside.