By having someone show you, while videos are great, having someone doing it in front of you and than helping you with the placement of your fingers and the amount of pressure needed is better.
In most cases people do not apply enough pressure which is why they do not pop animals successfully.
After that once you learned from someone it's all about practice and doing so on animals of various sizes.
I would not someone doe does not know how to pop probably does not know how too probe and probing is not something that should be attempted by someone that has not learn how, it can lead to injuries and best in this case as well is to have someone teach you.
I very rarely probe the only time I ever probe is a BP is with a tensed adult otherwise I pop everything else from hatchlings to adults.