Mr. Wolf just told them to do the obvious
They was standing around clueless as to what do after killing Marvin, and they act as if Mr Wolf is gonna show up and solve their big problem with his expertise, but all he does is tells them to clean up the crime scene DUH! and wash the blood off themselves DUH! and gets them some different clothes DUH!
They couldn't figure out to do all that themselves? two professional hitmen?