When refinishing fiberglass, the only paint stripper I use is my DA(dual action sander) and 220 grit paper.
I have tried a few "fiberglass safe" strippers. They definitly didn't harm the glass.....
Of course, they barely harmed the paint either!

So, now I knock off the majority of the paint with the DA and 220.
After the 220, I make any necessary repairs.
Then, I hand sand with 320. (block sand large areas) Next, a coat of filler primer.
That gets sanded 90% off. Then fill any imperfections with micro-ballons and epoxy.
Prime again. Wet sand with 400. prime again. Wet sand again to a nice consistent satin finish.
Part is ready for paint.
Good luck!
Doug