I believe most of our car washers used to be part-time before the creation of combo jobs, then they became fulltime positions to satisfy the 22.3 language. Since then they have significantly cut back on car washers and has even "laid off" existing combo employees who were doing car washing as one of their two jobs. As said before they are usually positions that go to high seniority employees since they are seen as easy jobs, but the chance of you getting one depends on your building, and area language regarding them.