It's fairly simple once you get the hang of it. I watched a few videos on YouTube and tried it on a known male. Took me a few tries to get it to work. You have to roll the tail forward like a tube of toothpaste. The flesh should be a lavender color and the hemipenes should be red.

If the flesh starts turning red, stop. If you haven't gotten anything by then, you're either doing it wrong or have a female. If you don't have more than one snake to practice on, give it a day, to be safe, to rest before trying again.

You should get it on the third or fourth try. Also, smaller snakes are easier than larger snakes to pop. Probing is usually better when dealing with a large snake.