Once he gets a taste of squirrel hunting, at some point taking a hunter's safety course would be beneficial---it'll probably pique his interest even more and empower him to know what "the lay of the land" looks like across different types of hunting. Based on descriptions of what it's like to hunt different game animals, he might be able to choose what he wants to try next after squirrels.
There's of course no other way to learn well how to hunt a new type of game than by doing, but first you need the inspiration to go after it, at all.