If an avatar flies, falls or jumps onto my prim, I want it to slow them down - and, ideally, bounce them gently upwards - as if they had fallen into water or something soft & squishy. Pushing them back up doesn't work, as they still end up in an undignified position

llGroundRepel looked like a good idea, but I got confused by the parameters. I don't want them to have to attach a hovering widget. Is there some way to achieve the effect I'm after?
Thank you

Cherry