Sorry, Steve, but I disagree on the pressure washer. Too many h/o use too much pressure and end up doing more damage than good. Yes, we can tell them to use low pressure, but too many ignore that advice.
Instead, I recommend a non-chlorine bleach oxygenated cleaner. PDC (premium deck cleaner) is one brand. Follow directions for mixing and applying. After it sits the recommended time, just spray it off. The results are amazing.