My current board has no finish or anything on it, so I periodically wipe it with rubbing alcohol (keep clear of any varnish...) and then give it a very light swipe of mineral oil. I know some like to put a drying oil or some other finish on the ebony; if that's your case then a solvent probably isn't a good idea. Don't eat PB&J while you practice, though its worse on bow hair than fingerboards...
Oh and steel wool and scotch-brite pads are abrasive, so if your board is polished nice and shiny they'll dull it.
