Use your finger or switch hands to decock? I carry Sigs and I'm left handed. I use my finger. Decocking is not a time critical skill like reloading on empty or racking the slide so the extra second or so to switch my grip slightly at the conclusion of a string of fire is no big deal.
if you're concerned about decocking in a self defense situation - I would say this: when in the middle of a gunfight do you envisage it would be either prudent or necessary to decock your pistol? Decocking is something you do when you are finished with the pistol, either because you have finished shooting or you are out of ammunition. In either case, it won't matter, because the fight is over, or the pistol is empty, so you can take your time.
