I usually just use a damp, clean cloth(no soap) once or twice a year to periodically clean my guitar. If my guitar ever got dirty enough, I guess I'd use a couple of drops of mild dish soap in the water,but I've never needed to. I would never apply a wet cloth to my strings.And that's an aweful lot of polish on the back of the neck, IMHO. I wipe my guitar down with a clean, dry cotton cloth after every use, including the back of the neck. That's all I've ever needed to keep mine nice and clean. I don't see why anyone would need to wash or polish their guitar everytime they play it. I wouldn't want all that soap all over my guitars, nor that much polish on the back of my guitar's neck. Put the soapy cloth and the polish bottle down and step away from the guitar
.(just funnin') Really, it'll be o.k. If you're worried about soap residue left on your hands from washing them, don't. If you wash your hands, rinse and dry them, you'll be fine.