On the job training. Entry level pin setter mechanic training is fairly basic (Lock out tag out procedures, basic machine operations, simple trouble call resolutions (ball returns, re-spotting pins, that sort of thing)). Usually you'll be working with a full mechanic, learning how to do various repairs and preventive maintenance on the machines.
I'm working with the Brunswick A2 machines. Here's a link to the service manual if you're curious what these machines are like (PDF): https://brunswickbowling.com/uploads/document-library/Servic...