I sometimes tell my students who are blowing through their air by waving their arms around and kick-kick-kicking nonstop that they're "working too hard." It seems like a nicer way to say it than telling them their technique sucks, and after all, they can't help being awkward beginners, can they? Certainly relaxing and just letting it happen is a great air saver.
Sometimes your SAC rate can be linked to your OW training, talk with your buddy before diving, make a dive plan. get familiar with your buddies dive gear. If you haven't smiled or laughed alittle bit a few hours before your first dive you might be stressed alillte. test and trust your equipment and don't use your inflater valve as a elevator lift or a tv remote control, attain neutral bouncy asap and then just relax "Yoga " good point. A bigger tank is just a quick fix at best..work on relaxing and being comfortable underwater, then a bigger tank will pay off big time. Men there is no way to compete with Women's SAC rate ( no pun intended) I don't think you have to have 100+ dives to develop better breathing skills, just go back to the basic training you learned in OW and try to apply it to yourself.
Bubski