if the scuff is on already I don't bother. When I remove the scuff, I normally sand down and will put a little wax on both sides. I then put a new scuff back on. Regarding losing moisture it all depends where you leave the bats. I lost 0.4oz from leaving it in the car for the whole summer, hardly a disaster. Likewise, leave the bat in a damp environment and the moisture content will go up, making the bat heavier. The bat can take on moisture as well as lose it. I would keep an eye on the bat weight from time to time but unless it drops dramatically I wouldn't worry too much.
The other thing that's maybe inferred from interweb is moisture is lost in different places. Losing moisture from the face is far more of a problem than losing it from the spine. After all the spine doesn't normally hit the ball. Hence the advice on not oiling if a scuff is on.