Finished up the sewer cover today. I thought it would be more daunting than it was after painting it all black, but in actuality it was quite liberating. Even though I was using a dry brush technique, it was fun to be able to be sloppy and dirty, not crisp and precise like with the rest of the piece. Even so, both pieces match the whole gritty tone, I think, and soon my realistic Leonardo will be completed!
Special thanks to Liv4EvrythgDie4Nothg for suggesting the rust and moss additions!