There are a bunch of nasty cleaning solvents out there, and Xylene is one of them, not good for your health, so I wouldnt recommend it, even though I have had occasions in which I did have to. Since the EPA and OSHA stepped in and took Trichloroethylene and Technical Freon off the general market, there has been quite a push toward the citrus-oil based cleaning agents, but they are rather labor intensive to use - a lot of rubbing and wiping, since they are a rather weak solvent.
But - there are still several good commercial solvents out there that are readily available from Lowe's, Home Depot, Ace Hardware, etc. To name a few there are Acetone, Stoddard Solvent, Naptha (Lighter Fluid), Xylenes there too but minimize contact, Trichloroethane, Methyl Alcohol (Corrosive to metals), and Isopropyl Alcohol. No mater what is used, the final cleaning step is: Moisten a clean, lint-free cloth, and wipe with Isopropyl Alcohol to remove any trace of residual contaminants and oily substances - there should be no indication of color left on the cloth when the last wipe is made. (Industry standard when cleaning precision Electro-Mechanical components)
