Topic: Deck Teak
I had excellent results with water and a stiff brush, followed by teak oil.
Wet down the teak so that it soaks up a bit of water, then scrub hard with the brush and your usual deck soap. The waste water will be black but the wet teak will look great! Rinse, and then let dry for a day or two. The teak will appear to be light brown instead of weathered grey. Occasioinally I have had to rescrub a section where I did not scrub sufficiently.
Time commitment -- I usually do this at the beginning of the season during the first deck cleaning so it takes two to three hours (including cleaning the deck!).
Then lots of teak oil and the boat looks like a million bucks. To do the teak oil I usually plan on several hours on board. I use a rag and wipe on the oil which the teak sogs up like a sponge. The rag is important as it works lots of oil into the wood but ensures that you do not spill too much oil on the deck. Teak oil leaves a residue that can be cleaned but it is an effort.
By going around the boat and starting again right away I can get in about four coats without too much difficulty. The teak sponges up whatever oil you apply.
I usually put on one coat of oil during the season as maintenance.
It sounds like a lot but it is really just part of the cleaning regimen for the deck. A neighbour recently spent three days taping, sanding and Cetol-ing his hand rails -- far more effort than my scrubbing method. And we have more teak!
I have no idea what will happen if you try this method on partically Cetol-ed teak. It may be necessary to sand first. Maybe leave it all to weather for a season to remove the Cetol?