Hi Shooter,

You have two questions here,

The 1st point, Lag, I find the best way to feel lag is to seperate the hands on the grip(about 4 inches apart) and swing normally you should feel the lag and the wrist rotation, also this can help with the correct follow through.

Your 2nd point drills for the follow through extention, if you tee the ball a few inches past your left foot and swing normally you will have to extent to reach the ball.

If you are finding it difficult to feel the extention it may be because you are trying to feel it during the swing, extention is natural if you are relaxed.
Try swinging the club first then evaluate the swing after, not at the same time.

A good tip for practice is to hit every shot with a clear mind then assess what you did or didn't do after, everyone can remember what they did a few second ago.

Hope this helps


Ian.