I DID learn to sex snakes. I have a set of probes and I sexed all my snakes when they arrived. I just had my experienced friend watch me as I do it as I am not confident and also to double check me. I think that is a good idea, no? I learned to pop too but I can only pop babies I can not pop adults properly. I don't have THAT many snakes to practice on as I am just starting out, and it is probably not a good idea to probe every snake many times. So I have been trying my best.
Every time I had probed the snakes under my friend's supervision, I had gotten the sex that it was sold as immediately. Of the two males I had, both probed deep my first try. I am very surprised especially since my friend double checked me and he has been keeping and breeding since years before I met him, and I met him six years ago.