If you don't already own one of the many commercially available pressure washers for a homeowner, you can rent one from your local home center. Seek out the highest GPM (gallons per minute) machine they have available. This will make the job go considerably faster. The pressure is not important as high pressure should not be used to clean wood. A simplified analogy is to think of cleaning a dirty dish with a spray bottle (higher pressure/lower flow) versus using the water from a faucet (lower pressure/higher flow)
Damage from using high pressure can vary from splinters and raised grain to visible lap marks in the wood (these show up more after sealing) Just using a pressure washer without a proper detergent like Restore-A-Deck can also yield unwanted results. The pictures below show examples of a homeowner using no cleaner and just high-pressure water to clean.
After you have allowed the oxygenating power of Restore-A-Deck to work its magic, it's time to rinse. While you are at the home center renting your machine, try to have them give you a nozzle which will lower your effective pressure to 800 psi. If you do not have access to interchangeable nozzles, you will need to keep the tip of your gun at 12-18 inches from the surface.
Start the flow away from the wood surface and bring the gun slowly into the position to start rinsing. Start at one end of a board and walk your way to the opposite end keeping the nozzle the same distance from the surface the entire way. This will prevent lap marks. If for any reason you need to stop in the middle of a board, start the process from the beginning (at the end of the board) until you pick up where you left off. Take your time and always keep conscious of the distance between the spray tip and the wood. Be extra cautious on spindles.
When you are finished cleaning, apply your brightener and rinse. You may use the pressure washer again or a hose may be faster for you. No pressure is necessary during this final step.
Note: You may experience some small fuzzies that appear after the wood dries. This is normal to a small degree (especially on cedar). Often times these will dry up and fall away during subsequent rainfall. If you are planning on sealing as soon as is possible, these can be sanded away.