I think most DIY er's use the foam roller and brush method when applying two part polyurethane
. The paint is very toxic when atomized in the air with a spray gun and requires a fresh air respirator if you don't want to have any nasty side affects. You can get good results from the roller and brush method but it does take some skill and technique. As Chuck said preparation is the key and you will spend most of your time fairing the hull. The painting goes quick. If that high gloss new car finish is not the most important thing you can add flattening agent to vary the finish from gloss all the way down to flat. I did this when I painted my trimaran
and I came away with a nice satin finish. It helps to hide the minor surface imperfections. The high gloss will show up every scratch and dimple that you may have missed in the prepwork. As some mentioned to me as I was fretting over fairing the hull some more, "just get it done it's a boat not a German piano". I used Interlux
over a 15 year old Imron paint job.