Post-processing and filaments for weather-proof electronic enclosure
There are already some questions about the choice of filaments for outdoor use:
Which is more durable to sunlight/weather - PLA, ABS or PETG
3d printing for outdoor use: what types of filament are most weather resistant?
PLA use outdoors?
It may very well be that if you print in PETG you won't need any postprocessing.
If you still want to, you could try to paint or spray the outside with some bitumen spray for car underbody.
I think that the only part which actually needs postprocessing is the spot with exposed moving parts.
It's difficult or impossible to find a solution without having an idea of what we are talking about when you say &quot;some moving parts exposed&quot;, but in general this is solved first of all by adapting the design so that water wont' be an issue: rain should flow away without getting inside, and spatwater should be reduced so that it will evaporate when rain stops.
If you only have an exposed pin for rotating parts which are inside, you could also pour some wax: it will seal it while allowing movement. The same bitumen spray may help.