6061 is easy to get a matte finish. Bead blasting and anodization is the best way to do it.
The process that ILLusion Kinetics uses leaves a slightly brighter finish than your image:
The entire unit is oxidized to a matte finish, and the sides are then honed to give it that shine. It's possible to leave the entire slide in a matte finish if required. See the top portion of the slide as an example of the matte finish possible.
Kevin, let us know how that Duracoat finish works out. I'm interested in knowing how well it holds up.