Yeah, dish soap will cut all the wax on the car right off. Some sources say that ph of the soap isn't too kind on the clearcoat either, but I'm not sure if I buy that. At any rate, if you are going to use dish soap, I'd rinse liberally and then wax it several times right after. It is something to consider if you got gunk embedded in your wax and you don't feel like using a claybar.