Most of the OTC products work extremely well.
The white strips from Crest work extremely well. That's probably all you need. Do a test run and see how you react. If you react well, then try this: Keep one set of strips in for atleast 40 minutes and then do a second set of strips directly after. This will make the process faster. Your teeth may be sensitive and you may have some white spots on your teeth or gum irritation. This resolves very quickly.
There is also Watts high concentration peroxide gel on Amazon which you put in a tray, but it is difficult to use because the gel foams and gets liquified from saliva and is hard to hold in the mouth. It works though. Advantage over the strips is that you can make all teeth whiter.
Arm & Hammer toothpastes with baking soda and peroxide are really good for maintainence.