we have a 3/4 wrap-around with 4 sets of stairs..... cedar..... i feel your pain facing a large project....
because we are trying to catch up on all "deferred maintenance" in order to sell the property once there is even the slightest recovery of the housing market, we have done the back half this past autumn, using sikkins products, which are a bit pricey but have a high quality.....
the brochure from the product line instructs the homeowner to clean the decking surface top (AND bottom for the initial application) by treating it with a cleaning solution of bleach and tri-sodium phosphate (TSP) and then powerwashing..... we used a 3 gallon garden sprayer for cleaning and stain application.... it totally sucked under the deck, but otherwise it is the most efficient method we could devise
so far so good..... thank god the cold weather came and we had to stop!!! but i can tell you the difference between the cleaned and stained portion and the still to be done section is AMAZING......
for the record i tried to convince the hub to use extruded wood composite but i was over-ruled so now we are paying an additional 2 grand to spiff the deck up for someone else to enjoy.... go figure