They are not difficult to put in. You use a fine gauge needle, like 22g or 24g, and inject medical grade sterile water, after swabbing the skin with an alcohol wipe, about 1ml (enough to make a big-sized blister) subcutaneously. He would see the skin rise over the bleb. It needs to be sting-y feeling, and it needs to be enough in each one to make a half a pea-sized blister, or a little smaller. I do four of them, over the sacrum, about 4 inches apart, 2 on either side of the spine, about 4 inches away from the spine. The relief is usually fairly instant, and lasts about 2 hours.