My wife has Secondary progressive MS and is confined to her powerchair during her waking hours.
In order to keep her as dry as possible because of her incontinence, I put the night time Depends on her all the time.
I also put a water resistant pillow cover on her cushions that she has on her chair.
Sometimes when she gets very wet, before I can change her, it will leak through to the cushions.
To prevent it from soaking the foam rubber, I get the disposable bed pads (Depends brand) and cut out the little u shape at the back and line the cushion with it before putting the cover back on. I keep 2 sets ready to go, while washing the covers.