It is a fun trip- done it twice, also 10 day trips. You need good rain gear! August is usually the rainiest month in AK and July is the warm up session. You need good rain gear!
This page provides current and historical water levels, and other data. It is near the Dry Bay takeout point.
Most people go to Haines to rent their rafts and equipment and get shuttled from there to the start point in Canada. Canadian rentals are available too. You'll need your passports or passcards.
The expensive part of the trip is the pickup flight. The best option is Yakutat Coastal Airways. Hans has a turbine Otter, which works great for supporting Tat trips. It works best if part of the group goes back to Haines with the gear. If you have more than half a dozen people and 2 rafts, some will need to go back to Yakutat with Hans. He picks up the Haines bound people and gear first, then picks up the Yakutat folks on his way home. Yakutat is actually a much better place to get a connecting flight (than Haines) since AK Airlines flies a 737 through Yakutat every day.
Alaska Charter Flights and Flying Service - Yakutat Coastal Airlines
We had this guide book, which was helpful. Someone else brought it- don't know what they paid for it but the price on Amazon is now $138!!!
Did I mention that you need good rain gear?

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Good luck!