You don’t need a cassette opener, as when you rewind the film, listen and feel for it coming off the take up spool and then stop. In this way when you open the back of the camera some of the film leader will still be visible. You can then pull out about 6”, as you probably wasted this amount when loading the film into the camera. Cut the leader off and load the first 6” into the spiral in daylight. Thus making it easier to do the rest when in the bag.