I have tried popping pretty much exactly as the video you posted (thank you!) shows.

Are the males that you're popping definitely popping male? Also, I will usually pop when they hatch, then wait until after the first shed and pop again to make sure. I've found that with hatchlings it doesn't take much pressure. If it's a male, you'll know it...Just make you're noting it down on their feed record to keep everything straight.
None of the hatchlings I have popped have popped male. 5 of the 7 hatchlings have been popped (the other two are still in egg) and all have popped female, which I thought was odd. I'll have to repop after they shed just to check and see. Upon visual exam and palpating, I don't feel anything that would indicate male, I'm just obviously a little wary to think that all of them really are female!

Probing in all forms makes me nervous, but less so with a larger snake. I think I'd rather avoid probing if possible with these tiny guys.