the one process that will remove all the grease (and the paint too), but requires completey disassembly of the machine, is the a "jet washer" at an automotive machine shop.
I kind of like the patina on my 60 year old south bend lathe...scrubbing it half clean with mineral spirits is good enough for me. This solvent requires good ventilation, and the soiled rags are flammable, but it's not quite as bad as kerosene, and not nearly as bad as lacquer thinner. And it won't get all of the grease off, just the top layer, so the lathe will still look old when you're done cleaning it up.
have you searched the web for info about this? there's at least one
South Bend Lathe forum out there.