FWIW I am not a huge fan of always using detergents to clean kegs.
My theory is that if it started clean and was filled with clean beer than it's still pretty close to clean. I think complete disassembly is crucial to remove hops particles or yeast sludge, however.
So, I take the thing apart and use a brush on the dip tube. Inspect and soak (in hot water) the poppet valves and the in/out posts and lid. Then I power rinse the inside with a garden hose and handheld sprayer. I carefully inspect the inside and if it's clean, then it's clean. Reassemble and add about a quart of starsan. Pressurize. Shake to completely coat the inside. Attach a picnic tap and drain a little starsan so the dip tube gets filled with sanitizer. Then store until needed. It's good to go on demand up to months later.
Now if there's visible gunk stuck to the inside of the keg, then you have to mechanically scrub it and probably need Oxyclean.
Works for me.