The most performant way is re-making your face gestures to include the animations for the ears/tails. The second most is duplicating your current gesture from the fx layer, adding a new layer that looks initally identic, changing the neutral/blank to an empty animation or an animation where ears are in the default location, followed by replacing the animations inside the other faces with whatever files you bought for the ears according to how creator labeled them to match.
The simplest way that makes its own FX layer for every animation is using vrcfury gestures, + animation, and putting every animation clip inside however the creator made them to fit to the gestures.
