I think you were using a backplate+wing (bpw), since it comes with a crotch strap?
With a bpw, like what sibingai mentioned, it's easier to descend by leaning backwards. Doing that pushes the air from the bottom to the top of the wing where the inflator hose is connected to.
The bpw is never comfortable on the surface, it's made for underwater use. A properly adjusted crotch strap should hold the bpw in place on surface, even though it can be painful on the crotch after spending a long time floating around. If it feel like its going to lift over your shoulders, it's provably a sign the crotch strap is still too long.
With regards to weights using a bpw, if you have only a weight or two, try putting it on your tank strap(s). If you still want a ditchable option, wear the weight belt over the waist belt and crotch strap, after putting on the bpw. It can be quite uncomfortable though.
Sent from my iPhone using Tapatalk