I didn't have the time to paint it when I put it together last summer. It's aged some (it went under cover during the winter rain, but still), and has some dark streaks on it. It's on a hot front porch, and it gets good and backed every day, so if it had mold on it (quite possible) it doesn't have an active case now. I want to put primer on and then paint it, but was told to clean it first. No idea what the wood is, it was a kit from Ace Hardware. How do I clean it, what product to use?