In my experience, do not use Slick Sand over DP. I shot an engine compartment with DP90, came back a week later, scuffed it, and shot Slick Sand. It softened up the DP, and wouldn't cure. I had to sand the entire engine compartment down again, and just shot it with Slick Sand. They make a product called Feather Fill, with all the properties of Slick Sand( high build, easy to sand) that was created for just this reason. That is what I would use over Dp.
