Is it full size or small? At any rate, I use small golf practice balls from about 5-10 feet in front of the hitter. I am behind an L screen throwing overhand. Then we switch to the pickle ball station. Then they go live situation or an at bat vs a pitcher or a coach.
The most common sponge balls I see are those little Skilz balls or I see kids flailing away at a yellow nub on the end of a stick held by someone.
It might be fsster just to ask the person you see using them