At the end of each sefer we say chazak chazak v'nitchazeik -- leader first and then the congregation is what I've seen. There is some uncertainty in my mostly-lay-led minyan about exactly when and how this is done, and since it only happens five times a year and I'm mostly with that minyan, I haven't had the opportunity to see how others do it. I'll be the torah reader the next time this comes up (in two weeks), so I'd like to avoid the usual "um, do we do it now or...?" problem.
Who says this -- the ba'al koreh, the oleh, or the sh'liach tzibbur?
When is it said -- at the conclusion of the reading before the closing b'racha, or after the b'racha?