I have a River Rok aggregate finish gunite pool that was done about 3 years ago. The plaster was not done well as there were some bad washout areas after exposure. Bottom line is I'd like to repair some of the really bad spots. Any idea on if I can just buy a bag of the River Rok plaster and go over these spots or do I need something else? I'm not too concerned if the spots are a bit noticeable. I just want to stop the kids from hurting their feet.