+1 mineral spirits, which is exactly what WD-40 is, except it's cheaper by the gallon.
+100 on the spray brake cleaner. Absolutely the best gunk remover there is. Evaporates to completely dry in seconds. Expensive, though. Caution: it also is very tough on your hands, so use gloves.
Simple Green is good, but really should be water rinsed, which might make it inconvenient. Buy it by the gallon and mix up a stronger solution in your sprayer.