there's not much to it really.. fairly straight forward. just push the needle in 'til the point is all the way in (make sure you're pushing into the nipple and not really deep into the breast or anything) and inflate until it hurts too bad to continue.. nipples are very resilient where that's concerned, I've inflated mine hundreds of times just for the pain factor + having huge nipples for a little while heheh. you only need very little amounts to get significant size increase, like <5ml even on the high end, so it's fairly safe if you follow sterile technique.
this is fun and interesting,
i have injected saline under my areola by inserting at the edge and the pushing the needle under my nipple but still in the areola. makes some excellent puffies!
jerry