West wind. You said automotive spray paint…
I cannot emphasize enough test. T e s t. TEST the surface being painted. These paints are becoming more environmentally friendly but I’ve seen some of these ruin plastic and other surfaces.

It’s easier to test instead of strip.
There’s my itty bitty 2 cents

Good question Westwind. I guess we all have our own preferences, and who's to say one method is better than another. I find that my solution sometimes is dependant on what materials I have to hand.
After many failed attempts I now know how to use a spray can of paint and get a reasonable finish. Sometimes this has been on top of brush applied primer or undercoat which has been rubbed down before applying the next coat.
In the knowledge that water will ALWAYS get inside a boat I make sure to paint or varnish or flowcoat the inside surfaces thoroughly, and preferably in white or a very light colour to help with future work or bailing out.
In the case of your fibreglass hull my choice would be to spray the exterior (with whatever your choice of paint is) then to brush coat the interior using white flowcoat. On a plastic cabin I would opt for spraying, only because you should get a better finish than brushing, with less effort. I might however brush paint the cabin interior because you have better control without the need for masking.
Good luck with yours😉

Well, I now always a ‘2 pack aerosol’ paint. You will get an excellent finish and is hard wearing. The cans appear much the same as an ordinary automotive spray, except there is an additional button at the base, when pressed, allows hardener to mix with the paint. The downside is, the paint is only good for (I think) 2 hours, so everything has to be prepared before you start. Follow the instructions carefully as this needs to be used in a well vented area.

I use both methods as well as dry brushing to raise detail. I spray most plastic and fiberglass parts. On wood finish with yacht varnish I use a brush sanding between coats. time and patience are a must. Dave RR