I learned this from a mechanic about 20 years ago. It works GREAT.
All you need is some Q-tips, toothpaste, and carb cleaner.
1. Smear a very small amount of toothpast onto the top of the Q-tip. Rub it in gently with your fingers so chunks of toothpaste don't end up in the fuel passage.
2. Insert the Q-tip into the seat and rotate it back-and-forth a few times. Then use the other end of the Q-tip to clean the residue out.
3. Hold the carb upside-down and spray the seat with carb cleaner to remove all of the toothpaste.
4. Inspect your shiny, clean seat. :i_am_so_happy:
(http://i5.photobucket.com/albums/y177/Lotsokids/FJ1200/Seat_polish.jpg)