I use boresnakes, gunscrubber (for tuff stuff) and a good old Tee-Shirt with CLP on it to wipe it all up with. On internal workings I like to spray a bit of RemOil on it. I guess it depends on how dirty they are to begin with.

After each use I clean mine prior to putting them back in the safe. If they remain unused for any length of time, chances are they will just need to be wiped down and have some wax re-applied.