I played golf for a long time. In fact before lifting became my passion, golf was. I come from a golfing family (my father was the president of the local country club) and started playing very early.
I'm actually not fond of explosive rotational movements with med balls. I feel that they actually detract from the coordination of a golf swing.
I had my greatest power on the course when I started getting serious about the olympic lifts. I feel that the explosive and whole body nature of the olympic lifts transfer well to golf power. Obviously these must be learned properly, ideally with a qualified coach, to be effective and safe.
I really like how long drive champ Jason Zuback trains. He basically lift like a combination of an olympic lifter and powerlifter... one could say that he trains like a shot putter. And to be honest I feel that shot putters/discus throwers share the most similarities with golfers when it comes to training needs.
Sure you need a VERY strong core/abs. But your power will come from the hips, legs and torso and you need to build a lot of strength in these areas with the big basic lifts. I feel that gold training tends to be too "cute" and "gimmicky"... of course since most golfers do not have an extensive background in hard training, it's probably safer and easier to have them do cute exercises.
On a side note, the strongest athlete I've tested on preacher curls (we used the Poliquin Structural Balance test which included testing preacher curl strength) was a 165lbs golfer.. he actually tested higher than linemen from the Rams and players from the Blues with a 205lbs strict preacher curl.