I have a lot of problems in this area, too. My tonsils stayed infected because of the post nasal drip. The crypts would develop stones. Nasty smell, etc. I had my tonsils removed, after many years of suffering. It took some convincing, because doctors are reluctant to remove an adult's tonsils. Even with them gone, I have problems with throat infections due to the PND. This is gross, but what helps me is to use hydrogen peroxide to clean my throat, especially any folds of skin where bacteria can get trapped. I use a q-tip with peroxide on it and then wipe the back of the throat. You can also use your fingertips (after they are very clean).
Another, very different, thing I've done that seems to be effective is to place a bit of fresh ginger root in my tea every afternoon. I boil the water with about an inch of fresh, peeled ginger root in it, add the tea, and then let it set. It tastes very good.