Foam or fibreglass can be slightly shaped with a heat gun, you’ll want to gentle with it though. Or with foam you can use a sharp blade to trim areas and add or take away material then use contact cement to glue the seams together again. I wouldn’t recommend hot glue if you want to keep the seams clean and invisible. If you sealed the foam prior to painting the heat gun can also heal wrinkles in foam. Any deep tears will have to be filled with something like dap or do what turbo says and turn it into extra weathering.