Use new and fine bristle toothbrush. Actually the phone's speaker membrane is located at the mesh/grill side, with tiny balls to accentuate the sound. It's safe from the bristles.
Better not touch/clean that area of the phone then, if you're doubtful. If you drop by any Samsung Service Center in your place, you can always have a technician clean it if you think it's too delicate for you. Samsung staff will be happy to assist 😀. Any grumpy Samsung staff that won't help, you can always post his/her photo in this Members site 😂
