Hi Alvin - I'm glad that you bring this subject up, as I'm curious how others will respond. Here are my responses, not to be confused with Yogani's responses!
In other words, I'm not sure that mine are correct, but here goes:
1) I just take one deep exhale/inhale and then continue with the next round.
2) The index fingers stay at the eyes, pushing in at the corners throughout. So they stay in place, the only movement being the middle finger, which pushes in to close off the nostrils. Which in part answers the next question....
3) I wouldn't do it where others could see. [8)] It's an awkward practice, with elbows jabbing and chin bobbing, not to mention the odd configuration of fingers. But besides that, I don't know why you wouldn't just do it with your regular practices, as it only takes a couple of minutes.* My intuition is that it's good to do it with everything else. And I'd hesitate to do it more than twice a day, as these practices can have a delayed reaction, and you might easily overdo.
4) Good question! I thought it was specifically for energy, so I'll be curious to hear what others have to say.
* except if you're breathing more between rounds, which'll take longer.