The inside is sealed and should be washed periodically with warm water. A good option for "sterilizing" the inside of the didj is to mix up a strong saline solution and pour it into the didj - let it sit for a short while, and then rinse.
The outside has a fine coating of essential oil over the epoxy; this can be renewed with oil, wax or polish. This will make the wood finish shine.
The mouthpiece may be treated with essential oil (including tea tree oil in the mix provides a natural antiseptic).
The mouthpiece can be shaped as desired with sandpaper and then oiled.