Since it sounds like you have some experience painting, you already probably know that gloss paint has a much harder finish than flat. If it were me, I'd paint it in gloss, and if you want to dull down the sheen, put a satin, or flat clear over it. Flat will make it hard to get mud, crud out, being so porous, but a nice satin will be easier to clean and still look good. If you clear it with satin and decide it's too shiny still you could mix some flattener to dull it more. Black accents would look great either way, IMO... Good luck with it, and post up some pics!