There are so many variables in moisture problems.
1) Location, do you live in an extremely humid loacation? That will affect moisture getting into your guns.
2) How you fill. This covers a lot of ground. Is the gun above the low point of the fill hose? That can keep moisture from "rising" to the gun. Do you have a cotton filter to stop liquid from moving into the gun? Do you use desicant? Do you fill fast or slow, take breaks, etc?
3) What do you fill with? A hand pump is hard to pump fast enough to build up substantial heat and precipitate moisture in a large volume. Do you use a slow compressor Ie., a GX or similar? They don't fill fast and build a lot of heat. Does you compressor have any moisture mitigation built in?
That's just a few of the problems that can crop up. The truth is, and combination of them can cause problems, but all can be mitigated should the need arise. I filled with a GX for a long time, and never had moisture in any of my guns. I live in WV where moisture is not a big deal, so that's likely the saving grace. I now use N2 fed to a GX and that works like magic and no, absolutely NO moisture, so no worry.
If it's me, I would choose a method of pumping up my gun ie. hand, compressor, scba, whatever, and then use it and check my gun for moisture from time to time and let that be my guide on filters, and moisture mitigation. You can't argue with results.