>>76586928
A lot of people dismiss them but I find bent over flys are best for hitting the rear delts specifically. It's much easier to go heavy with rows but you're engaging so many additional muscle groups that the load is spread around and the extra weight doesn't translate to as much additional stimulus to the rear delts as you might think. If you do the flys with strict form instead of cheating and emphasize the hold at the top of the motion moderate weights will still blow your rear delts up