I had a few garments that needed some help with DWR and I got a Nikwax pack of Tech Wash and the TX Direct wash-in DWR treatment. The TX Direct looked and smelled like PVA-- polyvinyl acetate, AKA Elmer's Glue or drywall sealer.
Could it be possible that it is PVA? I am NOT recommending that someone go out and dump their $300 XYZ ultralight panties in dilute Elmer's glue, but the prospect is interesting.
Dilute PVA drywall sealer might be a better place to start-- at your own risk. I would try some scrap cloth first.
Does anyone know what kind of stuff is used for DWR? Inquiring trail stompers want to know!