Antibiotics will kill off the good bacteria in his flora. He will need probiotics to reestablish this. A supplement of MSM will also be helpful to help mend tissue. Since the mineral content of our soil has long depleted, a mineral tonic will give his body the tools necessary for repair. A diet of as many fresh raw fruits and vegetables as he can eat will also increase his enzyme content in the body.
Attention is the key to visualization.
The more attention he gives the area that needs healed, the more his body will respond. He can imagine anything he likes regarding healing. Have him visualize things like little cartoon characters carrying materials to the wound. Or have him visualize himself as healed and running and playing. You can get technical and have him visualize red blood cells depositing healthy tissue and white blood cells carrying away infections.