It's all digital from what I've seen. It seems like some clear epoxy would work well. Maybe some mineral oil after it cures, just to help fill little gaps (since epoxy tends to be pretty viscous).
EDIT: Although epoxy makes it a bit difficult to change the battery, depending on how you go about it. Maybe some conformal coating on the PCB + mineral oil.
EDIT: Although epoxy makes it a bit difficult to change the battery, depending on how you go about it. Maybe some conformal coating on the PCB + mineral oil.