Pour-and-drain conformal coating as an alternative to potting
I've used Plasti Dip for very small quants w/ success on assembled boards &lt;1 in sq. about 3-4 years ago and the assemblies have lasted to the present. I don't know how this would scale for larger boards, or for production.  I used it because it wasn't a big deal if it failed, fast was more important than right, and I bought it off the shelf. Of course, if this is mission critical I'd recommend much more research.

Dow Corning has a conformal coating tutorial  that you might find useful.