I'm not sure about making the bra dynamic. It can be done, one of my free Vicki 3 dynamic clothing packs has a dynamic bra, and BillyT has some dynamic lingerie on the market. 
The main advantage is not having to fiddle with oodles of morph dials to get the bra to fit - and doing the same the next keyframe, and the next, ad infinitum. But it certainly is more difficult to model well.

The pen is mightier than the sword. But if you literally want to have some impact, use a typewriter

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