Bro:
First you need to be evaluated to as what the problem is and which muscles are affected.
Most commonly it is a muscle imbalance between the large torso internal rotators (pec, ant. deltoid & lats) and the cuff muscles - primarily the infraspinatus and teres minor.
you need to make sure of the alignment of shoudelrs, scapula and head of the humerus. Strengthening the external roators is only part of the solutiion. you may need to stretch the internal rotatos (only if tight - DO NOT stretch muscles that are not tight), stregthen the exteranl rotators AND usually the scapular retractors.
A strong cuff is useless if it is misalingned and the shoulders internally rotated and the scapula elevated - the typical forward head, caveman, benchpress fanatic posture.
also DO not train internal rotation unless you have a weak or damaged subscapularis or you will just increase shoulder internal rotation and worsen the condition.
Good articles and books are: Big bench, bad shoulders & surviving the big hit by Paul Chek and the 7 minute rotator cuff solution by Dr. Joe Horrigan - I'll try to find some links.
You might also wish to investigate ART therapy
S