Just make sure your rap sounds natural, as in, something you would actually say in real life, however, It has to make sense too. Example: This guy told me in a battle he would SMACK GAY FAG UP. What's wrong with that multi? It's forced, moreover, he would never say this in real life. You would say; I'm gonna SMACK THIS GAY FAG UP or simply, SMACK THIS FAG UP. Most likely, he just stringed together those words to rhyme with a specific multi set, and this made the ending result forced.