02 Dec 2014, 22:33
You could try it with q-tips and alcohol for the dirt and with vinegar essence + time (30-60min) to let it soak in for the rust. It's a bit tedious, but I think it should be done, especially on an Alps board with a (presumably) rather thin plate. I have a keyboard here with Alps and a rusty plate and the rust has gone right trough the plate.
Just don't leave the vinegar essence on the keyboard for too long or it will eat its way through the plate itself. Check the progress every now and then, I've had some bad experience with a Model F plate and vinegar essence.