I think compressed air might work. Alternatively, I've tried using regular tape and just getting it to grab the stuff that's fallen through the holes. Cheers.
Since the bottom of the speakers (and keyboard, for that matter) are covered by the black film, you'll simply be pushing those dust particles under the grill/mesh. I'd try the tape route first.
as mentioned earlier, the holes arent actually "holes" a hoover wont do much because there isnt a way for air to get through the holes...its blocked by a black film. But you could try!
I'm having the same problem, and the same thoughts about how to fix it, but I haven't dared trying anything yet
What about using a vacuum cleaner, but hold the black film back with a needle or a toothpick? I'm figuring it /should/ work, but I won't try it with the hoover on full blast