I know you stated matte black, not flat black, but here is a guide from e90post.com for anyone interested. Damn I thought I was the only one contemplating this! If only I had gotten the jump on you. Best of luck with it though! I'm excited to see the results (and I might be doing just the roof of mine as well )
http://www.e90post.com/forums/showthread.php?t=376442