I am no coach or swing guru and may well get chastised, but I have used the following drill in the past. With no ball present as a practice swing. Take the club to the top of your swing position and pause for a fraction of a second. Then drop your hands straight down keeping the left arm straight. Drop the hands to about waist height. You will feel the right arm come down in to the right side, if your stance and posture is good your elbow should ideally be beweewen your stomach and flank. This is the pulling the chain motion, this is how you want your arms to react when the swing starts but this is not the trigger, this is the feel you want after the start. I do this about three times. This will instill the feel of the arms dropping in to plane.
Now take the hands to the top and start the swing sequence. This starts with a slight hip bump then your left hip should start to pull back around the torso, starting to work back against the solid base of the legs and feet. As the hips start to open the hands will hopefully follow the move you have just rehearsed and start to drop down in to the slot. The hips continue to work round and form that position the arm will follow the rest of your body till you then release the club head in to the ball and hey presto. The right side of your body will start to come trhough and drive up to a finish position.
When all is in sync and you are hitting the ball sweetly I can only say that when you swing you really feel as if you are hitting the ball with your entire body. You go to the top, trigger the hips aginst the lower half, the arms just drop and follow through with the entire body, it is almost effortless and you need to have the basics right. Grip, stance, posture and alignment.
I used to have a terrible problem coming over the top and casting with a fade being the outcome or weak slice with the driver. I would attribute this drill being one of the many things that helped me overcome this but is a drill I often revert to.
Hope it helps.