Really no need to do direct oblique focus movements, weither it be side bends, bar twist, etc. High reps are just wasting time if you want to lose fat around that area. Watching and adjusting the diet has the most bearing on the fat content around the powerful oblique muscles. If you want extreme core strength ( lower back, abs & obliques for example) for heavy lifting and athletics than by all means use a DB and alternate side bends from side to side. Using a 100lb DB + after a short period of time is not out of the question for these short range & powerful muscles. For most men the obliques are not a potentionally large muscle group (as are the abs not overly large by nature) even when well developed and general ab work has a strong bearing on them. Obliques are worked with most exercises anyway, from overhead lifting, cleans, DL's, squats, all forms of pulls/chins,, rows,etc. Also included is boxing & martial arts where quickness & twisting in throwing a blow is vital, even leg/knee strikes. One of the better core strength (oblique/abs/lower back) exercises is the old one arm bent press, a real athletic challenge as well as the alternate overhead DB side press.The ancient Greek and Roman cultures regarded a heavy set of obliques as a very masculine trait. Good Luck.
