Don't worry too much about cleaning perfectly. Just whiting over the text and writting there is good enought.... except for when the text is ovr the head of charscters. Then you can do the lazy translator's trick of putting a semi transparrent rectangle in wich you write the english over the japanese
Touching live wires is ok if the current ain't strong enough or that there is a conductor that is attracting it.
When you touch something else along with the wire though...