Hey Mike,
Your right there are a lot of different opinions out there, so let me throw in my two cents worth, hope it helps answer your question.
1. How long should you wait to clean & seal a new deck?
You can actually clean and seal a new deck almost immediately, just as soon as the wood is dry enough to accept a sealer. Unfortunately some deck builders still tell people to wait 1 year befor sealing, Man nothing is further from the truth (maybe in the old days). I tell people if they seal their deck within 2-3 months after its built and keep it clean & sealed that their deck should look like a hardwood floor. If they wait too long the wood starts splitting & cracking.
2. What to clean with and how much pressure?
This always the real controversial question, I would probably suggest that a first time washing would be to use an oxygenated bleach powder mixed w/ water (Disodium Peroxydicarbonate) My company sells it as "Safewash" real cheap & real good.
The pressure to use I would say 300-700 psi you can go as high as 1500, but there is no need too. The days of powerwashing wood are over, nowadays we are letting the chemicals do the work.
3. Millglaze, This is where I usually ruffle a lot of feathers,in our industry, but who cares, it works.
I find that the millglaze I normally encounter is on the support posts, 4X4's or 6X6's. At the mill they use dull blades when cutting these which burns the wood and closes the pores, this turns the wood rather black. (for those that didn't know )I have tried every way possible to bring these posts back to clean & brite.
The one chemical that I have the best luck with is strong bleach, (yes that nasty ol chlorine bleach word" You can actually watch the wood return to brite right before your eye's. After applying this let it sit maybe a minute, rinse it then neutralize it with an acidic solution (normally oxalic acid 5%)
Now like I tell everyone, If you don't like to use bleach, don't. To each his own.
Mike I hope I helped, please stop by and visit our web site someday, we offer chemicals and sealers for wood guys like us.
www.sunbritedecks.com Thank you Chris Detter