Howdy
In my own, very biased opinion, fanning is just a bad thing to do with any revolver. No, probably a little bit of fanning will probably not damage it, but think of how it will rip up the palm of your hand as you drag your hand across the hammer spur.
Also, unlike slip hammering, there is very little control of the revolver when it is fanned. The guys who compete in Cowboy Fast Draw are always shooting blanks, never live ammunition. Despite what you have seen in the movies, there is less control of the revolver when fanning than slip hammering, or firing conventionally. The physics of fanning a revolver requires it to be fired from the hip, so precise aiming is not possible. And slamming the hammer with the palm of the hand will cause the barrel to wobble all over the place, so accurate shooting is pretty impossible. OK if your opponent was right in front of you, but it would be difficult to hit him if he was more than a few paces away.
Fanning a revolver is just a bad idea, in my humble opinion of course.