For the screw threads, use only the type of contact spray that completely evaporates so it leaves no residue, as it contains only propene (used as a propellant) and isopropyl alcohol. So-called "protective", anti-oxidation and/or anti-corrosion types of contact cleaners are to be avoided on the screw threads excepting only after you have stored the parts unscrewed for so long that oxidation buildup needs to be removed from the screw threads prior to cleaning them with isopropyl alcohol. Be advised that these so-called "protective" layers of electrically conductive lube/grease need to be completely removed from the screw threads in order to help prevent corrosion. This lube/grease can be removed with isopropyl alcohol, but the best strategy is to always completely avoid having to remove it, i.e. by simply not putting it on there already in the first place, if possible. So avoid storing the parts unscrewed. If you're going to store the parts, just leave them screwed together tight instead. The screw threads will thank you for it.
That said, yes of course a tiny little bit of oxidation occurs each time when you unscrew the parts to change out the battery or when you switch atomizers, due to coming into contact with oxygen from the air you let in. But no, this does not normally become a problem in any way whatsoever. Because, by unscrewing and screwing back together, this tiny little bit of oxidation is effectively polished away, and, the resulting tiny amount of oxidised metal dust ends up along the side of narrow gaps that, due to tolerances in the machining, exist between the screw threads. This dust will remain inside these narrow gaps until it is removed with regular maintenance. The reason why it is perfectly harmless inside these gaps is simply because no electrical conduction happens across the gaps anyway in the first place, i.e. it is because narrow gaps filled with air do not conduct current regardless of whether the gaps contain small dust and air or just air. Finally, it should also be noted that frequent polishing of the screw threads by keep rubbing them with metal polish and polishing cloths or microfiber towels or etc. is never a great idea in the long run, either, as the excessive removal of metal through frequent polishing will widen the gaps between the screw threads until they no longer can provide contact properly... thus the voltage drop of the mod will only start to worsen faster─when compared to normal wear and tear alone.