Well I have never tried it but Chip Foose said on one of the episodes of Overhaulin that you always use the same or softer materials to come in contact with the trim. This is so you dont stretch the aluminium or stainless or whatever, for instance if the trim is Aluminium, you would use an aluminium or wood tool to tap with a hammer to straighten it. Also dont do it too quickly or hard as this can heaten the area and distort it more.
Hope that helps, but dont blame me if it doesn't work