[Ed]

Before you sand anything, you really want to treat all of the wood with wood bleach (oxacylic acid) so that the color is consistent throught. Wood Bleach is available at just about every hardware store. Best thing to apply it with is a chemical grade spray bottle. Be sure to wear a mask as it breathing in the vaporized acid is not too fun.

After treating with the wood bleach, you want to make sure that the teak is super dry. You can leave it out in the sun for a week or stick it in a room with a dehumidifier.

Once it is good and dry, sand as mentioned above and the topcoat with a one of the numerous products on the market.

Good luck.