http://news.carcareproducts.com.au/2013/06/21/how_to_care_for_matte_paint_and_wrapHere you'll some advices for matt paint.
I had the matt black on my Harley Fat Boy Lo (black denim)
I just washed and dry it (with pressed air and a soft micro towel)
Any wax and polish will damage the matt effect.