If I told you, I'd have to kill you. Good injections, painless injections, are one of the best internal marketing techniques in the business. And trust me, you will get on a roll with IAs (Im on a 3 month roll right now) where you dont miss. And then you have the week of hell. The biggest frustration I have, in all of the daily bull**** I deal with is when someone isnt numb. Its amazing how simple it is to piss you off. But, when I have scheduled #18 MO, 30 minutes, and i always inject and wait 10 minutes ( second molars dont work well with septo, you have to block),you sit down, lips numb, cut, ouch....Im pissed. . As far as painless injections, find a mentor and good topical. There are tricks, and its not about shaking the lip.