I use a washing up bowl, fill it with maybe two inches of warm water. I dampen the rat, then shampoo using baby shampoo (preferably the non-tear variety - but keep the shampoo away from their eyes and ears). Rinse off the shampoo and dry well using a towel (or hairdryer on a LOW heat setting)
Lots of people use a bath-tub (I find the bowl easier because I don't have a big bathroom) or the sink.
Hope you're not afraid of getting wet, they like to share their bath with you (I always end up as wet as them afterwards)
Well first Lilly died of a tumor. And my other little girl Ping Pong (lol funny name, its just she is always everywhere like a pingpong ball ) died with blood in here "private part" probably from an UTI (urinary tract infection)
R.I.P. Lilly and Ping Pong
I've become quite the expert at baths (I only say this because others have! ). I don't recommended anyone who's not extremely experienced in wriggly rats try my method, tough. I've gotten down to 2 minute baths at the sink. But I do end up very scratched up, heh. My advice is always to have everything ready before bringing the rat in.
Anyhow, remember that rats do bathe themselves and for the most part, they don't need a lot of baths. Too much bathing disrupts the natural oils in their skin/fur that keeps it healthy. That said, the occasional bath is fine, but do prepare to end up scratched! Some wear a long sleeved shirt to minimize. Though, if you're lucky, you end up with rats that love baths. Rare, but there are some!
Oh! I just noticed you're in Louisville. Hello, neighbor!