Generally I do this for the other half of a ten gallon batch I'll just fill it and go, if I'm switching beer styles and don't have a clean keg to substitute I'll run sanitizer through it. But If I have the time, I like to clean it thoroughly.
I rinse thoroughly (including running hot water *into* the output port and through the dip tube), then put hot star-san in there for 10-20 minutes while I'm readying the rest of my transfer equipment. I rarely actually disassemble the keg parts for cleaning themselves.
To date I've had absolutely zero sanitation/infection issues across many, many keg fills.