I'm sorry, I don't know what happened but before you write the model off pick up some sandpaper (400, 600, 800 and maybe even finer) and see if you can salvage the model. You can find them at auto parts stores or hardware stores. Try wet sanding the runs a bit and see if you can smooth it out. Once you figure out how to correct the dull-coat application you may still be able to salvage the model.
Just a few things to consider. Make sure that it is wet/dry sandpaper and soak it for at least 5 minutes or more before using it. Keep the surface of the model wet as well and make sure you don't use a lot of pressure. Most of the time just running the sandpaper back and forth over the surface is good enough. All you want to do is level the surface, not take a lot of material off. Hope some of this helps you and good luck.
Ray