I clean an iron before or after a shot with a wire brush if I notice it needs it. How many times depends on the course I'm playing and the conditions. No set routine.
I wipe off my driver face if I feel like I am not hitting the sweet spot (so I can see where the next impact is). On days when I'm really hitting it well it never occurs to me to wipe it off and on days when I'm hitting it like crap it might be after every shot.
If I'm at the clubhouse waiting for our game to start (and I'm in the mood) I sometimes take all of my clubs out of the bag and clean them in the lake that is just a few feet away from the clubhouse.
A few times a year just before golf trips I clean them all in the kitchen sink.