Don’t use force in screwing. Substitute rather fuller contact. You can screw into the middle pocket from the baulk centre spot off a ball on the centre spot of the table without bringing it back into baulk.
Try the effect of extremely light handling of the cue even to the extent of making merely a loop of the thumb and first finger and allowing the cue to lie loose there. You will be surprised at the life that this puts into the ball.
When the object ball is anywhere along an imaginary line starting 15 inches from a middle pocket and terminating in the centre of the table 24 inches above the baulk line a plain half-ball stroke with proper strength will bring it back to the same position.
When the object balls are a little apart in a line across the table near the top cushion, a screw cannon from baulk bringing the object ball in and out of baulk and back to the top cushion is a safer position shot than trying a fine slow cushion cannon off the top cushion.
The half-ball angle for losing hazards into a top pocket from either of the top and middle pockets is along a line drawn from the edge of the object ball to midway between the shoulders of the pocket as viewed from the spot, which is a very different thing from the centre of the pocket as viewed across the pyramid or centre spot.
Try how long you can play without (1) leaving an object ball in baulk, (2) losing the white in a pocket, and (3) the balls unintentionally kissing. You will find this good practice. Professionals sometimes make their 750 without either of these three things occurring, and it is because they scent danger from one of these sources that they are sometimes seen to hesitate.
Play every pot as if it were an in-off and every in-off as if it were a pot. In other words, never think first how to make the pot and the in-off, but where the ball played with and the ball left on the table are to come to rest. In five cases out of six the white can be directed towards the centre of the table, the cue ball left in a commanding position, or the red guided over a pocket as easily as not.
A position that the practised billiardist rejoices in and that the tyro somewhat shuns is the constantly recurring one when both object balls are about two feet apart in a parallel line half-way up the top side cushion and eight or nine inches away from it. The easy gathering stroke from baulk is a slow check side aimed half-ball, but taking the object ball three-quarter and gently drive the cannon ball also, after leaving the cushion with what is now running side. This is a basic shot, and billiards cannot be played without it.
Cannons are made with eight kinds of contacts, with and without cushion play in conjunction therewith, and each has its position uses. The eight ways are: (1) Fine on outside of both balls, (2) fine on inside of both balls, (3) fine on first ball and full on second ball, (4) full on first ball and fine on second ball, (5) full on both balls, (6) half-ball on both balls, (7) half-ball on first ball and fine on second ball, (8) fine on first ball and half-ball on second ball. The terms “fine” and “full” here mean finer and fuller than half-ball.