Bucket of warm soapy water. Dawn dishwashing detergent. Assorted brushes to clean the frame, charge holes, bore etc. Then rinse under scalding water and blow dry. Then, the whole gun gets dunked in my super secret solvent tank and blow/hang dry (in the summer, in Texas, hanging the gun outside for a while is the same as blow drying it)
I got the recipe from an old gunsmith. In a .50 cal ammo can, mix equal parts WD-40 and Kerosene. Add about 2 cups of Marvel Mystery Oil. It cleans, gets into every crevice and, when all the keroses and WD-40 evaporate, it leaves a nice film of Marvel (a light oil) all over everything.