Depends on the type of equipment. Service manuals help, but having a understanding of the design and why the builder added this and that is the key. That and good schematics. I was lucky enough to go through Navy propulsion engineering school and Engineman “A” school. I was also raised on a farm with a dad that worked as a fixer for Mohasco in their experimental lab. So we build a lot of machines to do what we needed. My brother is also a tool and die maker and we had a small shop. Take the time to study the machine and understand how and why it operates. It will serve you well.