Try oil pulling. Put about 1 tablespoon sunflower, sesame (not the toasted), safflower, or coconut oil in your mouth. Swish and chomp (not vigorously, but casually) for 15-20 minutes. The oil will get thick and foamy and then thin. When it's thin you can spit out. Spit out and rinse your mouth well. Repeat as often as you want. In your case, I'd do 3x a day for a while (can do back-to-back if you prefer).
See the oil pulling forum for more information, if you need it. Oil pulling is great for detoxifying the mouth, whitening teeth, and general oral health, even other health benefits throughout the body. Many people (myself included) have had bad breath and coated tongues cured this way.