A greaseman is a guy that can get you in. Also a guy that can make things happen smoothly.
In the movie "Ocean's Eleven", Yen was a 95 pound "little chinese guy", who worked as an acrobat in a Las Vegas show. He was so flexible that he could fold in half and fit in a very small tube in a portable safe. At the time of the robbery this is how he got into the vault of the casino. He got in, and therefore they called him the greaseman.
by Rick Ellis October 19, 2007