I dunno about katz's setup, but regular 'ole parallel compression is quite easy. Just setup a send on the relevant track, put your compression on the bus and set to taste, along with any other processing (I usually fairly drastically cut lo's and boost highs, but obviously it depends on the material and desired effect...and I usually put some distortion on it) and mix it back to taste.
Many compressors now come with wet/dry knobs, which basically let you do the whole thing in-track...but I don't like those as they don't let you do any other treating to the wet material.