That Moparts post is one of the most-read automotive posts on the web, and people have painted by Porsches that method. Don't try it without reading those posts and view the youtube's. Smart also to not comment until you read some of the posts.
I first did my camping trailer w/ roll & tip method, using a hard foam roller, foam brush, and Interlux Brightsides polyurethane "boat paint". A lot of area to cover and it came out smooth without any sanding, and is still shiny 4 yrs later. I plan similar for my 65 Dart. So far, I painted the trunk, applying it w/ a Harbor Freight HVLP spray gun. I will probably similarly spray the outside, but a foam roller would also work w/o overspray. It comes down to final sanding regardless of how you apply the paint. While probably not as robust as 2 part paints, boats sit outside in the sun for years so "should work" (and has for others). Judging from all the cars around here with failing factory clear coats after 10 yrs or less, I don't imagine it will look worse in the long run. It is sure easier to repair a 1 part paint, which is important in a daily driver. If yours is a trailer queen, better to go with the $10K shop paint job.
house paint roller.
