I know it's a really old thread. I get that. It's a timeless topic and a great question that didn't get any answers. It's power washing season. I've been power washing to "prep for paint" for 20 some years but I don't know for sure what solutions to use on different substrates to clean them if I'm not going to paint them. I have now access to tons of experience from pros specializing in the trade. I'm hoping some will be generous with their knowledge and let me tap into it. Most specifically what are the pros using to brighten up cedar shake roof shingles that have greyed? Thank you for your time.