I am thinking of a DSMB. I put a puff of air in it, which allows it to orient vertically. Then I put more air in it before releasing it to let it ascend to the surface. The air I put in it will expand as the DSMB ascends, so I don't need to "fill" the DSMB before releasing it; the DSMB will be sufficiently "full" when it reaches the surface. Easy-peasy. This is the approach I was taught many years ago, the approach I continue to use.
My primary DSMB is a Carter Lift Bags DSMB that I've owned since the late 1990's. Quite substantial. It will probably outlast me! I don't know if Carter still makes these.
rx7diver