[aleros_eat_rice]

Use mass air flow cleaner. Some sites will say use brake parts cleaner, but it's not for the maf.
There isn't really a coating per se, but when you have it apart, don't touch the wires or anything inside the maf.
The way I did mine was to wait for the car to be off for a minute, then I unplugged the maf. Next, I used a torx bit to take out the 4 little bolts holding it together. After it was apart, held the maf away from the car and sprayed the maf cleaner on the wires and rods in the middle until clean. Mine went from black to gray. You'll want to wait until the maf is completely dry before starting the car, but maf cleaner evaporates rather quickly, so it won't take long.
Installation is reverse of removal.
One other thing, make sure the arrow that shows flow direction is facing the same way on reinstall as on removal. The arrow direction is toward the plenum, just in case.