Sand in Paint I have a decent amount of experience with. I actually did so on my demo platforms when I was doing shows too. Just get cheap as possible exterior latex paint, but 100% make sure it is flat. (exterior paint is just slightly less likely to mildew which helps too) Sand, any play sand or bagged sand you can get from a home improvement store will do. It can be hard to mix in the can, I mixed it in the roller tray, and put the paint on super thick with way more sand than I needed and spread it by hand on top a bit too. Just do whatever it takes. A bunch of it will rub off right away, but a decent amount will stick. It won't last forever, but you probably need to paint outdoor obstacles once a year anyway.