how to fix pasty butt on tiny chicks?

i’ve seen people do it in containers where they cut a hole big enough for their head but not their body in the lid so their butt can soak, but this chick i have is so tiny im not sure how to handle it without hurting him. would a washcloth with warm water work? or anything else? i’ve never had a chick this tiny not even when they’re hatched so im not sure how to handle him.