If you want to remove the yellow waxlike coating (Cosmoline) you can use a Nylon and Brass Detailing Brushes. The nylon should be used on plastic and painted surfaces while the Brass brush can be used on the aluminum surfaces. Inspect your engine carefully to determine which components are painted and which aren't before diving in. A dampened rag can be used to wipe the surface clean.
Note, if you haven't cleaned your engine first you may want to before trying the procedure above. If you don't know how to clean your engine do a search in the detailing forum and you'll find great info. If you still have questions definitely ask before diving in.
