Really no need for training obliques if into BB'ing. If any fat is hanging around that area, than diet should be the main focus. (many classic Greek & Italian statues feature the muscular obliques as one of the highlights of the male body.... maybe than, but certainly not now) Though not a large muscle by nature, they still can get out of proportion when doing direct exercises for it. As Overload suggest, any overhead pressing, cleans, BP, squats, etc affect the obliques . As does regular ab training.
If your a serious football player (for example) and do not want to look like a pretty BB'er, than side bends can be done with a very heavy weight. Do them with a DB. Do one side at a time with moderate reps of 8-12. Do 2 to 3 sets max. Keep the free hand behind the neck. Side bends with a BB across the shoulders does not make that much sense, in my view. It's like using a counter weight, which is not desired. Quite a few track athletes train the obliques just as hard as the ab wall. Twisting/throwing events (and even running/jumping) like shot put, hammer throw, javelin need that exploding oblique power. Good Luck.
