Warwick surface finisher for the Warwicks, occasionally (every 29th of February). Anything else which is bare natural finish gets occasional beeswax (see above), lacquered gets a duster about as often as I dust anything in this house.
I don't seem to get muck accumulation on my fretboards - possibly because I mostly play fretless so there's no natural gunge build-up areas, but looking at the acoustic guitar which is probably the instrument I mostly play at home, there's no muck build-up from about 40 years of use. When I've bought instruments with gunge on the frets, I've used meths or IPA [1] to do the initial cleaning then some lemon oil to finish it off.
[1] Isopropyl Alcohol, not India Pale Ale (other ales are available)