I can tell you that no matter how many air filters you have, even the small pistol grip ones that attach between your brush and the hose, you will still get water in your brush if you spray to long. Adding a moisture trap directly on your compressor will not help, it will just take a few more min for your brush to start spitting.
I have the pistol grip moisture trap on mine, only so I can get a visual indication when water is building up in the hose. When moisture starts to build up I just take my moisture trap off, hold my thumb over the hose to let pressure build up and just let go to blast moisture out. I do this about 20 times to make sure I get most the water out, then keep brushing. I have to do this every 30min or so, but thats airbrushing. Also I do live where it gets pretty humid, so it is more of a problem for me.
I have talked to a friend who has been airbrushing photo realistic art for over 30 years and this is the same method he uses as well.