The methods listed above would work great. Personally, I wouldn't choose garlic as it is rather pungent in its smell, and if not diluted properly can make your skin feel like its burning.. like the sensation you get when you stick a whole clove of garlic in your mouth! Not that people do that often..
Honey is great for healing, and I would definitely recommend it. Here is a method I usually use for infected cuts.
First carefully clean the wound using a antibacterial of your choice. After this, topical applications lavender oil can be applied to a fresh cut or scrape, this will help to improve the rate of which your friend's tissue is healing; and will also help to kill germs.
To minimize scar tissue afterwards use tea tree oil. This oil also disinfects all wounds and can be utilized instead of the lavender oil if preferred. After the oil your friend has chose out of these has dried, apply cooling honey to the wound rather thinly, and let it dry.
Bandage the wound as soon as this has been carried out. To prevent infection from spreading, the bandages must be changed three or four times every day. In addition at each change of the bandage, further treatment can be done by spreading either a soothing aloe vera gel or a calendula cream directly on the wound before your friend applies the new bandage; this treatment will help in further relieving or in limiting the inflammation. This will also stop or halt the spread of infection, and lastly it will quicken up skin healing.
Hope this could help your friend,