How to fix an iPhone speaker that sounds muffled after long-term exposure to dust?

My iPhone earpiece and bottom loudspeaker output have become extremely quiet and distorted after working in dusty outdoor environments for several months. Calling on speakerphone or playing media sounds tiny and muffled. I tried increasing the volume and turning off noise cancellation in iOS settings, but the hardware grills seem completely blocked.

What is the safest step-by-step DIY cleaning process to dislodge embedded lint and sand without pushing debris deeper into the waterproofing mesh or puncturing the membrane? When should I consider getting a professional iPhone speaker repair service in Pakistan?