I did it one time back in 06. It works well, doesn't leave the oil pocket like most SEO's its painless, but I used a 21g 1.5 in. You have to make sure to do it all BEFORE they tan you or you will need to bring some pro tan to spot check those areas where you inject.
Its painless however and lasts for something like 8-10 hours. Pumps up the area pretty good, you will need to take in a small amount of water to help it, just enough.