A Large volume fat transfer for gluteal augmentation can be safely performed by experienced, well-trained and certified surgeons. None of the factors that you've mentioned such as IV vitamins, special diet, or Epsom salt baths make a difference for the quality of your fat transfer results. To achieve great results with fat transfer you must first be a good candidate with enough donor fat from other areas of your body and your butt should not be saggy with lots of loose skin, like after massive weight loss. Such patients often require formal butt lifting surgery (lower posterior body lift) in addition to fat transfer or gluteal implants. For fat transfer, I like using VASER liposuction for the donor liposuction. VASER does enhance skin tightening to the areas treated and the harvested fat is viable and very smooth for fat transfer. I recommend common sense post-op instructions to minimize sitting or laying on the butt the first 2 weeks after surgery to allow the fat to settle, and the compression garment is also used during the post-op period. I do not recommend any special massages for my VASER liposuction patients post-op.