Counting scales, looking at tail shape, etc is not accurate at all. While most might fit a certain rule, there are exceptions to the rule, which IMO makes it worthless.
And at 2 feet, I wouldn't try to pop a corn, they're not like bps that you can pop as adults. Once a corn is anything but a hatchling, I don't pop. I probe.
Probing a corn is just like probing a bp, fairly easy and straight forward. Best to get someone experienced to show you how to do it though.