@Capozhwm will elaborate, but if I'm properly informed, it's a process by which you use one specific type of sand and blast it into a used MVS shell or any other plastic part to make it look like new. I think in the plastic industry it's a well known process.
http://www.princeton.edu/~timeteam/sandblasting.html
So they will look like Metal Slug 4 shells, that are not shiny, right?. I do not really mind that look, kind of like it. But then again, I also like MS4, so what do I know?
Now, the question: will the multicart boards be compatible with original chells, both AES and MVS? I know some people would like to have transparent shells or something...