Strategies / Suggestions for hiring manual labourer for a niche Biz.

I would put more guardrails around the job instead of relying only on finding the perfect person. For example, if a tech is stuck for more than 15 minutes they have to call. No expensive parts get ordered without a second set of eyes. I would also use a paid working trial before giving someone jobs on their own. Sometimes the system has to catch the mistakes before the customer does