"Übung macht den Meister."
Freehand peening is much easier to learn, if you grew up using a hammer of some sort. I remember learning how to use a hammer as a young boy, from my Dad, and also from my neighbor who was a carpenter. It took a lot of practice for a young kid, to develop the hand-eye co-ordination necessary, to smoothly pound a nail straight into the wood, without missing the nail or damaging the wood. Whenever my Dad, or my neighbor was working on a carpentry project, I would be given some scrap wood, some nails, and an old hammer, to keep me busy and out of the way, but also to help me learn how. I was encouraged to practice. Learning how to use a hammer was considered an essential skill. However, that was back in the days before cordless drills, and pneumatic nail-guns. Now, even I seldom use a regular hammer, other than to occasionally hang pictures, or pound in fencing stakes. For most projects, I use screws and a cordless drill, because that way I can take it apart someday, and re-use all the materials. Cordless drills and pneumatic nail-guns have become so common place, that my local farm store recently put most of their nails on clearance. I still know how to use a hammer, however, and I assumed that everybody else does as well. It's such a simple skill.