Hey buddy !
So, it is pretty easy to paint on a fiberglass armor with what we have in France : just wash it with water and soap one or two times to get rid of chemical remains, then lightly sand it, then add some primer and let's go
You can get some non expensive yet very effective primer at Leroy Merlin.
The paint I would recommand is Montana, their Gold cans come in a very large variety of colors and I had zero problems with it painting neither on a Jimiroquai's shore helmet nor on ABS It's the only brand I use now.
I should be able to help you find the ones you need if you want.