I've been using this song to help baristas learn Size to Shot/Syrup ratios for years. It's been quite successful in reducing the time it takes to learn. Also, sorry about my hair it was a rough day, you know who came through.
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Also, just my experience, but try to make them feel as comfortable and safe as possible. It can be an intimidating experience to start a new profession, and it's incredibly important to make them feel like it is safe to make mistakes. That's how we learn, mostly. Unless it's just me and everyone else is awesome. Oh god.