A method I have used for years to clean all handguns works well for me, even when the gun is filthy.
Remove the grips, swing the cylider open, or the slide back and lock it in place, then surmerge the entire gun in dry cleaning solution (Varasoil, I think the spelling is correct), let it soak overnight. The next day I clean the bore, with a brass bore brush and solvent, put it back in the dry cleaning solution and use a shaving brush to scrub it, take it out and blow the gun dry with the compresor and shoot the oil to it, stand it barrel down and let her drain for a short period, then wipe it down and put the grips back on.
This is (was) the practice when firearms were being placed in long term storage while in the military. It has worked well for me.
The varasoil will make the gun appear to have a white substance all over it, that is just the absence of oil, the color will return once oil is applied.