In this case I’m not sure I would recommend what I did but I think its workable. I used both epoxy and then silicone.
Normally I would prefer a spray on silicone conformal coating but that would not work for the davega without some very careful masking of the screen and plugs. Too hard basket for me.
There are a couple of things that make conformal coating the davega trickier than your average PCB. The LCD and the gap between the two boards.
I used epoxy to seal around the edges of the LCD screen and the easy to get to contacts on the bottom. A brush on coating would be better for this as the epoxy tends to go on too thickly. I had to go back and scrape off some around the screw mounts so the davega would fit in the housing.
I couldn’t get epoxy into the gap between the two boards so I filled the gap with silicone. I had some on the bench so I thought why not.
The only areas that are not fully sealed now are the USB plug and the button and data plugs.
I did try to unsolder the LCD header to separate the two boards at first. But failed. I wouldn’t try unless you have the right equipment to do that.