grunzster once bubbled...
If you use the pull dump and lean forward isn't it still impossible to dump the air from the side opposite of the dump?
If the wing is properly sized and you are horizontal in the water there is normally no problem dumping air as the air can stll equalize from one side to the other. Very late in the dive with little air remaining I may on ocassion have to roll very slightly (maybe 10 degrees) to get the last bits of air to flow from one side to the other.
Actually listening for the air moving through the wing as well as through the dump valve is a good habit to develop and contributes to precision bouyancy adjustment and control.
The key to successfull dumping is not to get too far from the horizontal and, as indicated above, not to use a wing that is too large with the result that the tips float too high in the water. How much lift is too much for your particular configuration depends a lot on the wing design.
Some wings use a bungee system to reduce the profile of the wings and to help dump the air but this is a mixed blessing if not an outright curse. The bungee cords pose an additional risk of entanglement and snags particularly on some designs where they are taken to extremes and in the extreme they can make oral inflation difficult.
I use a backplate equipped Genesis Recon and the 75 lb wing works well with both singles and doubles. It uses two bungees sandwiched between the backplate and wing where they are pretty much snag free when used with doubles and this is as far as I would personally go with using a bungee system.
Using the back dump is in my opinion the only way to dump air as it requires no change in diving position and virtually no movement to make a bouyancy change. The resulting streamlining and minimal movement are a couple of those refinements in technique that will really help air consumption.
Many of the jacket style BC's available breed a lot of bad habits that work aginst being smooth and streamlined in the water. Moving to a set of wings is a great step toward really improving your diving technique.