Set up a straight in shot with a one diamond separation between the object ball and cue ball. (Use the paper reinforcement rings to mark the locations.)
Shoot the shot using the same stick speed until you can dead stop the cue ball five times in a row. (Make any necessary adjustments to your stance and stroke to achieve this, and then use those adjustments for all future shots.)
Set the contact point of the cue tip to the cue ball at exactly a half tip below center. With the same stick speed, repeat the shot and observe the draw shot distance.
WARNING: Advance ONLY when you have a constant draw shot the is repeatable (i.e., five exact results in five attempts). [And yes, this is boring, but critical to your ownership of a perfect draw shot.]
Drop the contact point another half tip (change the height of your bridge hand) on the 6:00 line. With the same speed, repeat the shot five times and observe the draw distance.
Drop the contact point another half tip (1-1/2 tips from cue ball center) on the 6:00 line. With the same speed, repeat the shot five times and observe the draw distance.
Repeat the process with a slightly higher stick speed until you can get consistent results with five different speeds.
When you own the speeds at the 1 diamond distance of the draw shot, repeat the exercise at the 1-1/2 diamond distance. Then work at the 2, 2-1/2, and, 3 diamond distances.
If you only work at this for an hour or two, you can settle for the slight improvements. But if you want true ball control, put in the full 20 hours it will take. You will be the envy of everyone who watches you pull off this amazing control. Railbirds will throng to watch your perfect draw shot.
If you get inconsistent results after several hundred shots and any adjustments don’t seem to work, get an instructor to take a look at your stroke fundamentals.