Most, if not all, pro golfers and instructors will point out the importance of the left arm (for right handed golfers; the right arm for left handed golfers). Ben Hogan was naturally left handed. He became a right handed golfer because he could not find a set of left handed clubs. I actually saw John Daly hit a ball 200 yards from the practice area with a fairway wood/metal, using ONLY his left arm.
Recognizing this aspect, one can buy weighted golf clubs and training aids for up to $200 each. Here is a tip to do the same, but it will cost you next to nothing.
Find any somewhat flat shaped piece of iron, steel, brass or lead that weighs 3 to 6 ounces. A tear-drop lead fishing sinker is ideal. Place the metal weight on the face of any old or used iron or metal/wood or driver that is hanging around your garage. With duct tape, securely tape the metal to the club. Use several wraps of the tape so that the weight will not fly off during your practice swings.
Now you can swing with your left arm only. Or you can swing with both hands, using your usual grip. Take a few swings daily with your “new” home-made training aid and you will soon find that you have better control of the clubhead because you have strengthened your less dominant hand. You do not have to hit balls, real or plastic. The purposes of the aid and the exercise are to give you more control, which will come automatically, as your strength increases.