I've come to learn that some people experienced having saline (you know... the implant filling liquid) directly injected into their breasts. It may seem very weird and scary, but I read it's quite popular in some countries to get "partyboobs". Someone (hopefully with a medical degree) can prepare an IV line and infuse it into the breast tissue. While perfectly awake and using no painkillers at all, it should be only a small sting from the needle, and the saline can be infused into the breast.
Saline being a popular filler because the body treats it exactly like any other body fluid and it will absorb it and you'll finally just pee it out. (They also use it to mix with medicine, so the medicine gets absorbed into the body and the saline will just disappear). I have no hard data on how long the breasts will stay filled, but I'd guess a couple of hours, maybe a day, depending on the amount.
I've been doing some research here and there and I've found it to be used most commonly in the BDSM scene. And with that I found a nice gallery so you can see the before-after.
This treatment should only take about an hour.
Is it safe? If the saline is treated using the sterile method, and the saline itself is sterile, it should be perfectly safe, since the saline is PH neutral to the body. The person injecting you should be skilled, or at least use common sense, while inserting the needle, just skilled enough not to hit any milk glands or muscle tissue. (And even then there's no real danger, it just hurts). Only thing that could really go wrong is not using the sterile method.
Anyway, enjoy this "other" experience:
As you can see.... other bodyparts can be inflated too