You can't decock or restrain the hammer. The whole point of the exercise is to absolutely ensure that there is not a round in the chamber, so even after you and the SO agree that there is not, you pull the trigger as one final test that you both got it right. Of course, if you use a gun with a magazine disconnector, you not only have to drop the hammer, but you first have to insert an empty mag in order to do so. I'm always a lot more leery of the gun that requires pulling the trigger to lower the hammer on a loaded chamber. Sure, there are just a couple of easy steps in getting it done, but do them just a little out of order, and it's an early trip home.