Problem with 6010 et al is not hydroscopic natiure of material, but actual
physial wicking of liquid into the product which is highly loaded with high
Er ceramics.  Sometimes sufficient hot water rinsing will be enough to get
rid of the residue, but you'll have to experiment with times, temperatures,
etc.

Suggest trying a product such as Arlon's AR-1000 which has a protective
barrier to keep process liquids in place.

Arlon is in Delaware at 1-800-635-9333.  Ask for Mark (there are two Marks
the one you want is in tech service).