Yeah, clean off the poop (some is black, some is not) and dry off the butt and fluff the fuzz around the butt.
If you cant pick off the poop or rub it off (gently) with a cloth or paper towel you might have to stick his butt under a running faucet of warn water. If that is the case, many people recommend using a hair dryer to dry off the butt as little chicks get cold very easily. I used a hair dryer a number of occasions, but no longer do so as there are just too many poop butts sometimes and they have all survived. (They did have, however, plenty of other chicks to warm up around). If you get super lazy you can take a pair of tiny scissors (I use one of those little swiss army pen knife scissors) and cut the poop off- it takes off the poop and the fuzz around the butt leading to less poop getting stuck on the fuzz.
Just be careful not to pull or cut off the vent tissue (where the poop comes out) - sometimes the vent sticks out a bit and looks like poop because it is encrusted in poop.
