^^^^Yes, check that topic out! Great exercises to do.
Also, for some visuals, you can check out YouTube. Dena Kirkpatrick has a ton of great videos. One of them is here.
And you can just click on her name to watch the rest of them.
Sherry Cervi also has a few problem-solving videos on.
Overall, you want to practice the turns slow to teach your horse how to handle them. You also want to be sure to give the correct supporting rein cues, leg cues, and body cues to help them make a perfect turn.
When you get to run with speed, things happen in a split second. Maybe you didn't set yourself up perfect for the turn. That's where leg cues and body cues come in handy to fix the turn while you are doing it. All those leg/body cues are usually subtle to the viewer watching and you don't actually know how the rider is communicating a lot of things to the horse.
It can take up to 2 years to have a finished barrel horse. So patience is key!