I got myself an ultrasonic cleaning machine(Father's day coming up...easy to accidently drop the suggestion that it looks better than a red necktie!).Warm water(90*F)+ a little Dawn,10 minutes then swab the gun with a brass brush and the front of cylinder with a stainless brush(for blued guns,keep using the brass brush),for aprox 1 1/2 minute of elbow grease then 5 more minutes in the machine.
It works for my 629...or any other guns and is almost effortless.
WARNING:don't put any plated gun(chrome or other plating))in an ultrasonic machine.It'll do a good job of partially ''unplating''your prized object!