Get a long dowel and put a sponge on the end of it with a cable tie like this.
It comes in very handy for those spots on the bottom that I cannot reach. Also, clean the kegs outside with some high pressure water to take care of the crude a hot soak in PBW cannot get.
After brewing, I fill my 20 gallon Blichmann up with water, heat to 160 degrees add PBW and it soaks clean in place. After an hour or so, I use the hot PBW to fill kegs for a soak too.