Any modern oil will do fine (I use Rem-Oil for light lube, barrel cleaner, and exterior preservative) for all your needs. You can, maybe improve by using a dab of high pressure grease on metal to metal joints (Mobil 28 works for me). For longer storage and/or field protection, a thin film of wax over the whole gun is good (Renisance Wax is my favorite).
Change oil and lube frequently; every shooting sesion if it shows dirt. Keep films thin. See above. Not all that much to it except to do it every time.
