G.P.
I am utterly opposed to putting soap in children's mouths or anything similar. I don't believe in "hurting their egos just a little". Respect is a two way street-- if you want their respect then you need to respect them, (fear of you is not the same as respect). The way I dealt with my children was to downplay it when they used a swear word and explain to them other and better words to use to express themselves. It worked fine. I've got two very polite children now. Please don't use the soap. That's a horrible way to deal with it in my opinion.