The soaps that used to good catfish baits were old Dove and Ivory. Then they started putting lotions, perfumes, etc into them. Not so good anymore.
IMO, use the soap to wash the blood and scales from cutbait off your hands. Good cutbait will outperform just about anything 90% of the time. That other 10% is where stuff like liver, hotdogs, and other commercial baits come into play.