IMHO, the best approach to effectively and efficiently remove surface rust is to media blast the rust away and then immediately apply a healthy coat of epoxy primer. The epoxy effectively prevents air and moisture from reaching any remaining rust in the pits of the metal and can plastic fillers can be applied directly to the epoxy primer. With this method, you dont have to worry about getting every bit of rust off the metal during the media blasting and as such can avoid damaging the metal.
