Hopefully one day when RL gets rid of 3DX and moves its functionality to CC, we would be able to apply this to CC characters.
Until then, if you really need to have a bouncing butt, or stomach, here is one, fairly simple way of doing it for Non-Standard characters with cloth.
For DAZ characters, I'd advise to run them through the Transformer in CC first.
Some experience with Blender is a must.

Not fully detailed to perfection, but would give an idea how to do it: