This is my simple set up for painting the topsides. This is one coat of white Easy Poxy:I've just applied red boot top and cove. This year, I went with straight semi-gloss. I'll probably go back to a 50/50 mix of semi and gloss.
Taping off is a large part of the job. Believe it or not, the actual sanding with 220 in a 6" RO sander and the painting, doesn't take that long.
I thin the paint and with a foam roller and a good brush, I'll roll and tip down one side, re-set the staging, and roll and tip the other in about 3 hours of pleasant(if I thinned correctly and the weather cooperates).
Usually, about 3' of area is what gets rolled-tipped, then move down the staging. The trick or knack is in the thinning, the timing and the airs effect on the paint.
Looking at this, I can see why the wooden boat style often includes no boot top and sometimes the cove stripe(if there is one) gets painted the same as the body. The reason; much less work to be done.
One important thing I've learned. I don't get too hung up on perfection in the boatyard. I still get a run-sag or two. And working outside, a few bugs will land in the paint, some bozo will drive by at 30 mph, etc.
Don't drive yourself crazy(unless you're a perfectionist). Once the boat is launched, there is no angle to see the same detail in the finish. The light, reflected off the water, hides most everything. And there's always next time, to do a better job.