Unless there is a problem with the rabbit grooming himself, rabbits really should not be bathed. Your friend can certainly brush the bunny herself. A good brushing will make his fur all nice and shiny. You shouldn't use grooming products on a rabbit because they lick and groom themselves and will ingest anything that is put on their fur.
If the bunny is matted and has problems, some groomers will help shave off his fur so it can grow back in. But that would indicate that the rabbit has been neglected.
A good "bent pin" puppy brush works well on most breeds of rabbit.