I had a foggy front camera too due to lots of dust ingress into the front camera housing. This was clearly visible in the front camera lens above the earpiece aperture - it was white instead of the pinpoint of blue lens. The best way to lift without the tricky lifting of the entire camera assembly is to peel back the large black sticky pad attached to the back of the metal display shield. Then you can roll the camera lens and proximity sensor out of the way and carbon fibre brush or air blast the dust out.