You can start by eliminating the feedings that are of least interest to your child (you can figure this out by how long the child nurses). Drop one feeding at a time and then wait a few days for your body to catch up with the signal to not produce milk at that time. Eliminating night feedings first may give you and your child better sleep.
At the moment, my wife has eliminated all the feedings for our 14 month old except for the 4am. This is proving to be challenging. For the past couple of nights she has given a bottle at that hour and plans to water down the milk by one ounce per night until the bottle is only water. She hopes that this will help our son's stomach to get the message that he shouldn't be hungry at that hour.
For the bedtime and nap feedings, you can first switch the nursing to the beginning of the bedtime routine so that it isn't the last thing before going to sleep. Then you can start completely skipping that part. Lately I've been bathing our son and reading the stories, then my wife does the tuck in. Our son has forgotten about the nighttime feeding.
For any breast pain associated with too much milk build up, you can try a warm shower, pumping a little milk out, cold cabbage leaves, or ibuprofen. It really should only take 2-3 days for your body to catch up with the signal to not produce so much milk.