I found both by brainstorming/researching riders and barns I would be interested in working for and sending them unsolicited emails with my resume.
I had no trainer involvement - at the time I was an amateur riding with a college coach who did not have connections to the types of barns I wanted to work at work. I targeted people who had something that attracted me. The first person I worked for also had a background in fox hunting and working with thoroughbreds, so I thought having that similar experience might make me more competitive as a candidate. The person I worked for at WEF I don’t even remember how I found. Possibly just looking at show results for WEF and looking at who consistently trained top-placing students.
Just do your research. Find barns and trainers you would want to work for and send an email with a professional resume. You may never hear back - or you might. The downside to this approach is you have very little insight into the situation you may be getting into and how the barn/trainer treats people. I definitely got lucky in that regard.
