I'd be interested in a write up on this as well. Actually, I've never heard of anyone cleaning the cats but if you figure out a way, let us know. I've seen cats contaminated from leaded fuel but those simply got replaced. I have also seen the ceramic honeycomb inside shatter from misfires. Some collapse into themselves and plug up the exhaust while others blow out which results in a cat inefficient code and possibly a rattle in the exhaust downstream.
I might end up finding those issues as well but hoping not!