Re-coating Deck w/Sikkens Cetol SRD

I stained my deck 4 years ago with Sikkens Cetol SRD and have been very happy with the results. My deck has a cover over it and where the sun hits it, the stain has faded a bit and could use re-coating. Problem is that the areas that do not see the sun are in great shape and still repel water. How do I go about prepping the entire deck for re-coating with Sikkens Cetol SRD? Do I power wash it and then do a light sanding overall to make sure that the new coat adheres properly to the wood? Any advice would be appreciated.