I would say it's something that can't be taught it has to come from within. This is a hard road to follow for someone with no musical ability....I would go out and look for other people doing what he wants to do to see if he can handle it.....and then dig in and take the years of preparation,rehearsal, backing track editing, or pay someone to create the song tracks & arrangements in the right keys, etc, and perform everywhere and anywhere to get the experience to fine tune the act before you even think of playing for paying customers...
this is a tall order that can be done, but it wont be easy.
good luck