Out of the ones you suggested, I would use AIO, definately. I actually have used an old brush head on my sonic toothbrush on the nooks and crannies of the key, because the sonic action really gets out trapped dust around buttons and stuff (I used it on my desktop stereo, it gets around all the little keys and stuff).
The little VW symbol could definately use some SG
The white lettering is gone (the indentations are still there) but that is why I only use the one key (so that the other one stays perfect). I would be tempted to paint some white out (or something) and rub off the surface (the white will stay in the recessed crevices, leaving behind the original lettering).
You know what I'll scan them both so other's know what I'm talking about.
So here it is. You can see how the white gets rubbed out of the indentations that holds the white ink. You could probably (just like on a tile) "regrout" the lines with whiteout or model paint.
For those of you who haven't seen the VW key/keyless control, yes it is switch blade style (press the silver button on the corner)
HTH-Steve