I use a thumbs forward grip, similar to the picture posted (not me). I disagree with gripping lightly, but you don't want a death grip on it either, if the gun is shaking you are holding it too tight. With a proper grip you can put shots center mass without ever looking at the sights.
Note: You do not want to grip a revolver like this. Your thumb would be right next to the cylinder gap which hot gasses escape from while firing. When you get into big boomers like the 500 mag, people have been known to blow chunks of their thumb off, there's pictures online if your stomach can handle it. I did this once with a .357 magnum and it burnt my thumb and embedded powder residue under my skin.