How to clean wood before maintenance coat

Greetings,

We applied restore-a-deck to our boat dock 9 months ago. We followed all cleaning and application instructions and applied 2 coats of stain. The dock looks amazing, but some of the heavier traffic areas are beginning to show signs of wear and we’d like to apply a “maintenance” coat. How much cleaning is required before we apply this coat?  (There is no mold or algae like there was before we cleaned it last year, and the majority of the stain is still good).  We live in Houston, Texas.  There is a roof covering part of the dock, but most of the dock is in full sun at some point during the day. The dock is 15 year-old treated pine (2x8’s).  We stained the dock with a Flood product several years before we used restore-a-deck, and the Flood only lasted a few months. We are happy with the restore-a-deck product, and want to extend its life. 

Thank you for your time, and please advise how best to clean and apply another coat to maximize the protection. 

bk