completely disassemble..does this mean you going to rebuild it or just remove the bolt on accessories covers and such. If you are going rebuild, home version..then hot tanking would get it done..however cam bearing and guides get a bit of eaten in the process..you can use red devil lye, please use all precaustion in working with this stuff...it cleans deep within the pores of the cast iron. Comes out looking like new..As it is cast iron, it is porous..and like a cooking skillet..numerous heat up and cool downs will impregnate the metal and will cause oil to eventually be under your paint again..that grease film is not because momma is not washing the skillet..it is coming from the inside out and coating the skillet.