For bullseye shooting, one handed. Concentrate on gripping the gun the same every time. Your hand should squeeze the grip fore and aft. Don't squeeze the grip from the sides. Especially don't have pressure with your thumb and pinkie. Undue grip pressure will throw your rounds every time. As you age, your ability to focus on the sights gets worse. I have to use corrected shooting glasses now to have a clear sight picture. Concentrate on the lines of white so it looks identical every time. And squeeze. Try to imagine where each bullet is going to hit the target with every shot. So you can make the minor corrections. Its you that pulls the shots, not the gun. Try to know with every shot, whether you have pulled that shot, and why.
And concentrate on every shot.
Practice, practice,practice, practice,practice, practice, practice