Hi guys, this is my experience with fiberglass painting and staining.
I work for a fiberglass door manufacturer name Epic Doors and we use a water based product called TruCoat.Us for painting and staining our fiberglass doors. It is made specifically for fiberglass doors so it doesn’t require any special primers, is super durable and lays down really smoothly.
I assume you can paint fiberglass boat as well as fiberglass is fiberglass. Worth checking! We are super satisfied with it!