Kill a squirrel (skin it) tie it on the end of a cane pole with a short line. Drag it up a tree and hang it in a short fork. Doesn’t have to be a big tree obviously.
Then take your dog to the tree and let him sniff around the tree, get him to look up and start shaking it in the fork.
Eventually I ease it down the tree toward the dog hopefully looking up at and barking at the squirrel.
I’ll let him sniff and almost catch it a time or two, then take it back up to the fork keeping the dog excited.
Shoot some quiet 22 ammo and let the squirrel fall and let him have it.
I’ve trained a few. If a dog doesn’t get interested in squirrels this way, he’ll never hunt.
Once he’s interested in them and starts hunting them, you have to just spend time in the woods with your dog to see if they’ll make a good dog or just ok. Which is ok too.