I came to trawlering from a small 19 ft Sea Ray runabout. My insurance company required that I get initial training from a USCG qualified Captain to ensure I knew the basics of navigation, conduct of vessels, lights and signals, boat handling and close quarters maneuvering. I also learned a lot about the local waters, best anchoring practices and hidden hazards.
It's normally a 20 hr course, but can be abbreviated when competence is demonstrated. Cost about $60 per hour in my boat. Once completed,the Capt provided a letter to the insurance company that documented our training. I gained a lot of knowledge through the training in addition to making a new friend. A win-win!