Buffing and matte finishes are incompatible with each other.
When it comes to protecting it, anything that leaves a residue, even if worked in to where you can't see it is going to start making it shiny.
If the paint is really well done you can use Windex electronic device cleaner/protector on it. It won't make it glossy and won't build up thereby doing the same the more you use it. It is harmless to plastics, glass, rubber and most painted surfaces but as usual, test before spraying it all over the place.
It isn't going to protect like a wax but then not much else does either. It will collect less dust and grit and what does get on it can easily be wiped off with a damp soft cloth like a micro-fiber.