How to properly clean dirty speaker grill the top one and the bottom s

Properly cleaning the top and bottom, two methods.

Basic way, use a anti-static brush, some use a toothbrush but I always take the safe approach, and gently brush the grills. Do not dig the bristles into the grill, so use a swiping motion.

Deep Cleaning, open device, pull speaker and mic component out, use compressed air to blow from inside out, brush if needed.

Keep in mind that if you're going to open the device you need to be cautious with the gold contacts and electric static discharge on the device. Mishandling can lead to improper functioning of the device. Follow the examples on Ifixit for dissembling the unit.

Do note that Apple has some strict guidelines about "tempering" with the device. If something were to go wrong it may void out any warranty services.

Good Luck