Many people think rats don't need bath, but a rat should get a bath once every six month, and i'll show you the correct way to do so.
First you will need a bath tub, or sink remember to always have a plug in the drain, because rats down a drain is not good. Well fill the the bath tub with luke warm water only about two inches deep, or less.
Step 1: Rat
Gently place your rat in the tub, but remember to watch out, and where a long sleeve shirt and gloves, because rats don't like baths they will use your arm to claw their way out. Let your rat get used to the water before starting the real bath let them play around first.