Remove all the items from the deck.
Using the low pressure tip on the pressure washer, apply deck brightener over the entire deck. Let it sit a few minutes.
Change pressure washer tips to a high pressure fan shaped tip. Clean from the tops of the railings down.
The water seal is a one-part mix. Apply it by using a pump-up pressure sprayer (very similar to an insecticide sprayer).
Note: The sprayer used must be made for water seal, as the seal will ruin a typical insecticide sprayer. Water seal will typically dry within an hour or two.