smash damage is typically started with heat to make the plastic mallable enough to bend it in (eg cigarette lighter) this is difficult to get realistic and fraught with danger (eg setting fire to the house or just melting a hole right through your model).
the second method is to use heavy foil to make a copy of the fenders etc needing damage, bend it up as needed and then back fill the foil with superglue&talc or epoxy (epoxy better) to maintain its shape. glue this in place of the plastic fender.
i think amt make a nice 5th gen (94)