To paraphrase seminal pool author George Fels, it's not doing things that builds your pool game. To build a straight-line stroke motion typically requires far less muscle effort and motion than most players presume.
I recently led my pool students to keep their shooting arm's thumb inside their pants pocket during the stroke! This and keeping the bridge distance minimal (2" or so) trains the mind a bit to make the smooth but small movements in great pool.
Place the cue ball on a line with a pocket, without any object ball impeding its path. Stroke it into the pocket with thumb in your pocket and a small bridge.
Note that you are forced to make a small but purposeful motion back and forth--you should be able to sink the ball even without any perceptible backswing. You are locked into a straight path back and through.
It is telling if you cannot sink or control the cue ball with accuracy. Surely then your hand/stick combination is off line!
An instructive drill for both reasons--alignment and learning that delicacy of motion wins the day for many strokes. Watch that pool ball sink more often, my friends.
