They will cure on their own over time, but I don't think that you want to wait that long, probably a year or even longer. If you are going to set it out in the sun, have it mounted on the car and all points in alignment for height and set as you can.
Fiberglass a memory to a point, you have to help it stay where you want it. Don't just set it out on a pair stands. Mount it on your car and drive it, it will cure.. Use good urethane primer that you can use bondo over , or epoxy resin and micro balloons as a filler. Sand it out and spray 2 or 3 coats of John Deere Blitz
black for your flat black coat. Don't make it a real wet coat it will be shiny. Three light semi dry coats will get you what you want. Dry flat finish that absorbs light, not reflect light. That is what it's for.
Someone will contradict me,, but that's what happens here.
Best of luck. You'll learn.