20'Fish Welcome aboard. I agree with what Reel said. Unless you are a painter, it is best hired out. There are some DIY "roll and tip" techniques for applying polyeurethane. Videos and such are on the internet.
RE: Your PM about my boat: My 20 was built as a cut down transom just like yours. After doing the rough glassing and attempt at fairing, I finally took it to a boat repair shop for paint. Van Wagoner Boats in Clearwater,FL. Thanks to Fred, Eric and Howard because they did a fine job on fairing and paint. It is Awlcraft 2000 over the Awlgrip epoxy primer. I can't remember exactly what it cost.

Some things are better off forgotten. The paint job is no show winner but if you saw what they had to work with it is very good. The entire boat was sprayed including the bottom. The liner was then taped and the non skid was sprayed. I know it isn't as durable as gelcoat but the hull paint is going on 12 years and the liner was painted 6 years ago. (Long project) The eurethane requires little to no maintenance to keep a great shine. It will chip, wear and scratch so eventually a re-do is in the cards as previously mentioned. Eurethane paint on a hull bottom is OK for trailered boats but I have been told the paint can let go if kept in the water for more than a week at the time. SO a barrier coat or some type of bottom paint is recommended for moored boats. My .02, keep us posted as to what you find out on pricing, the prep really is everything in a good paint job.