I agree with lsg that real soap doesn't work the best for washing dishes. Soap works okay for spot cleaning where you put a dollop on a wash cloth for scrubbing a dish directly. I do that a fair bit.
Soap does not work well if added to a sink full of water. Used this way, the bubbles will not last long, even with a 100% coconut oil soap. Soap used this way will also have a limited grease-cutting ability compared to a synthetic detergent cleaner. The best conditions for using soap in a sink full of water is if you have very soft water or if you add washing soda to soften the water.
As far as the zero percent -- I'm guessing you mean zero superfat? If so, yes, you can do that, but I'd probably use 1-2% superfat just to be on the safe side.