I've never seen it used on a body that was in good shape, but I have seen a couple of rusted Scouts with it. These guys just duct taped and fiberglassed the rust holes and applied the Durabak/Herculiner. It's amazing how well the rough testure covers imperfections. I have friends that have put it inside their body tubs and one that painted a hardtop with it(which turned out great, looks very good). If you already had rust forming, I'd recommend repairing it first. If you just covered it up, it could continue to spread under the liner and you wouldn't know it, until your truck fell apart

Happy Trails,
Chris