They're easy to pop. If you can do bps, then you can do corns. Biggest mistake is starting too close to the cloaca, make sure you start far enough down so you can get them to pop.

And if you're referring to any unhatched eggs, I give them a week, and if they haven't hatched, I cut them open to see what went wrong. Usually its DIE (dead in egg) and/or severely deformed. If they're not pipped within 48 hours, usually not a good sign.