I have never messed with Cedar, but a client that we do his rental houses is willing to pay the rate I want to drive down and do his private residence. What process/chemicals have you used to clean Cedar trim and Cedar siding?
Mix up a strong batch of sodium percarb for a pre spray. Spray it down, then pressure wash it out. Keep the pressure down as it will fur up if you’re too heavy handed and ALWAYS go with the grain or you will look like Zorro cleaned the place. Percarb is alkaline and will leave cedar dark so we like to follow with a oxalic acid rinse to give the color a good pop. A black pad can be used to remove furring if you end up with any.
The high PH of a percarb mix causes the untreated (not painted) wood to darken. Something to do with the wood tannins migrating to the surface I believe. The effect will depend on the type of wood you're working with. When you come back with an acidic rinse it neutralizes and you'll really see a difference in color with cedar. Out our way 95% of the power washing work is wood restoration.