Insta Rock, which has been out of production for year, it actually pretty good stuff. It's made of concrete grout, reinforced with shredded paper. You mix it up in a bowl and apply it with your finger or small spatula, to get the general shape of the rock face. You can carve in lines and other details when it's almost dry. It's no good for making rock molds but it works well for covering large areas, like railroad cuts, with a material you can make look like rock. A little goes a long way. We used it on a club I belonged to years ago, and four packages covered all out rock faces on a 96' x 30' layout. It does take a lot of hunching over, carving in lines to match the type of rock you want, but it takes stain well and looks good if you work slow and work from pictures of real rock. faces.
