First of all, I think that we all can agree that if we lived in a different society, the people who are marketing and selling TimberTech as "low maintenance" decking would be lined up against a wall and shot. And we'd all go to watch.
That said, here's the best cleaning regimen that I've found:
(1) Use Corte Cleaner (a powder, recommended by TimberTech; available at Lowe's for $25 per bag) according to the instructions to clean off surface dirt, mildew, etc.
(2) Then, for problem areas (on my deck, almost all of it), wet the deck with the cleaning solution, then sprinkle some of the powder around. But, instead of scrubbing it by hand on your knees (as the Corte Cleaner instructions seem to suggest), use an ELECTRIC FLOOR SCRUBBER/POLISHER. For me, saves hours of back-breaking work!
My wife donated an old Hoover to the cause; you can find them on eBay. Not perfect, but better than everything else that I've tried . . .
I should have mentioned that my decking is XLM River Rock. TimberTech got good reviews from Consumer Reports for mildew- and stain-resistance. Hah! Very disappointing. Even my contractor--a really good one--is surprised.
Anything you buy in America these days is more BS than fact...it's the only way the GREED MONGERS can maintain their billionaire life styles! They'll put anything on the package to sell it to you....."lifetime warranty", that's until you make it to the front door at the store your buying it at, after that, you own it!