See This Thread from 2006 discussing this very issue. It actually works better than you would think....
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In real diving, it's not very practical and you end up with more water in the BCD bladder than is typical when using standard technique.It may have to do with the technique of holding it basically parallel with the bubble in your BC while you are ascending. As the air in your BC expands while you rise any excess will come out basically keeping you balanced for buoyancy while you are coming up. If you have really good buoyancy there won't be very much air if any to come out while you come up though. I'm still a very new diver myself but I've worked hard on buoyancy. I may add a shot or two of air once I descend but it will be minimal. Even with minimal air in there I have tried this and it seems to work. I'm sure more experienced can comment on this technique.