From what I have learned, your shaft, excluding dings and whatnot, will get smoother as you use it because the oils from your hands gets into the grain. If you use to much dampness and it wipes away these oils, then it will take a short time to get the oils back into the grain so that it is smooth again. From people that I have talked to this is more of a theory than a fact, but it works for me.
It can also be that the wood is just damp and it feels like it is not as smooth at it was. I dont usually use a damp cloth wipe down my cue...I use a clean cloth, dry, and wipe it often just to keep the chalk out of the grain.
Another option is to take to a housepro somewhere and see if they can clean it and/or condition it - they have methods to make the shaft get that 'smooth as glass' feeling.
Anyway, hope this helps.
Chuck