Vent sexng is definitely an art rather than a science...... which is why even the most experienced sexers at the professional level, think hatcheries, have at most about a 90% accuracy rate. Here is an illustration that shows why it is so challenging, you can see that many of the configurations are very similar and then consider that you're performing this on the ridiculously tiny vent of a newly hatched chick, but as you said you can't learn unless you try
