I rarely have had an entire titfight in my bra, the entire reason of a titfight is mine vs.hers, having a bra on kind of prevents the natural feel and impact either has on her opponent.
There are occasions both start wearing bras more to see who gets pushed out of her bra or whose bra gives with the pressure and dragging motions, but honestly entering a room in a bra staring at each other and then stripping the bra off to show how full, firm you are to hers is more amazing then a duel in attire.
That said a breast fight in a silk robe, tight low cut spandex, fishnet body suits, or open cup bra is very sensual start to a long exhausting duel till one gives.